diff --git a/objectivec/BUILD.bazel b/objectivec/BUILD.bazel
index 4aa4b20..7f154ff 100644
--- a/objectivec/BUILD.bazel
+++ b/objectivec/BUILD.bazel
@@ -84,6 +84,7 @@
         "GPBRootObject.h",
         "GPBRuntimeTypes.h",
         "GPBUnknownField.h",
+        "GPBUnknownFields.h",
         "GPBUnknownFieldSet.h",
         "GPBUtilities.h",
         "GPBWellKnownTypes.h",
@@ -138,6 +139,7 @@
         "GPBType.pbobjc.m",
         "GPBUnknownField.m",
         "GPBUnknownFieldSet.m",
+        "GPBUnknownFields.m",
         "GPBUtilities.m",
         "GPBWellKnownTypes.m",
         "GPBWireFormat.m",
diff --git a/objectivec/GPBProtocolBuffers.h b/objectivec/GPBProtocolBuffers.h
index 9e081b0..fd38fde 100644
--- a/objectivec/GPBProtocolBuffers.h
+++ b/objectivec/GPBProtocolBuffers.h
@@ -19,6 +19,7 @@
 #import "GPBRootObject.h"
 #import "GPBUnknownField.h"
 #import "GPBUnknownFieldSet.h"
+#import "GPBUnknownFields.h"
 #import "GPBUtilities.h"
 #import "GPBWellKnownTypes.h"
 #import "GPBWireFormat.h"
diff --git a/objectivec/GPBProtocolBuffers.m b/objectivec/GPBProtocolBuffers.m
index b43cf7f..07cd400 100644
--- a/objectivec/GPBProtocolBuffers.m
+++ b/objectivec/GPBProtocolBuffers.m
@@ -26,6 +26,7 @@
 #import "GPBRootObject.m"
 #import "GPBUnknownField.m"
 #import "GPBUnknownFieldSet.m"
+#import "GPBUnknownFields.m"
 #import "GPBUtilities.m"
 #import "GPBWellKnownTypes.m"
 #import "GPBWireFormat.m"
diff --git a/objectivec/GPBUnknownField.h b/objectivec/GPBUnknownField.h
index 8835f4d..a145593 100644
--- a/objectivec/GPBUnknownField.h
+++ b/objectivec/GPBUnknownField.h
@@ -11,8 +11,25 @@
 @class GPBUInt32Array;
 @class GPBUInt64Array;
 @class GPBUnknownFieldSet;
+@class GPBUnknownFields;
 
 NS_ASSUME_NONNULL_BEGIN
+
+typedef NS_ENUM(uint8_t, GPBUnknownFieldType) {
+  GPBUnknownFieldTypeVarint,
+  GPBUnknownFieldTypeFixed32,
+  GPBUnknownFieldTypeFixed64,
+  GPBUnknownFieldTypeLengthDelimited,  // Length prefixed
+  GPBUnknownFieldTypeGroup,            // Tag delimited
+
+  /**
+   * This type is only used with fields from `GPBUnknownFieldsSet`. Some methods
+   * only work with instances with this type and other apis require the other
+   * type(s). It is a programming error to use the wrong methods.
+   **/
+  GPBUnknownFieldTypeLegacy,
+};
+
 /**
  * Store an unknown field. These are used in conjunction with
  * GPBUnknownFieldSet.
@@ -26,48 +43,127 @@
 /** The field number the data is stored under. */
 @property(nonatomic, readonly, assign) int32_t number;
 
-/** An array of varint values for this field. */
+/** The type of the field. */
+@property(nonatomic, readonly, assign) GPBUnknownFieldType type;
+
+/**
+ * Fetch the varint value.
+ *
+ * It is a programming error to call this when the `type` is not a varint.
+ */
+@property(nonatomic, readonly, assign) uint64_t varint;
+
+/**
+ * Fetch the fixed32 value.
+ *
+ * It is a programming error to call this when the `type` is not a fixed32.
+ */
+@property(nonatomic, readonly, assign) uint32_t fixed32;
+
+/**
+ * Fetch the fixed64 value.
+ *
+ * It is a programming error to call this when the `type` is not a fixed64.
+ */
+@property(nonatomic, readonly, assign) uint64_t fixed64;
+
+/**
+ * Fetch the length delimited (length prefixed) value.
+ *
+ * It is a programming error to call this when the `type` is not a length
+ * delimited.
+ */
+@property(nonatomic, readonly, strong, nonnull) NSData *lengthDelimited;
+
+/**
+ * Fetch the group (tag delimited) value.
+ *
+ * It is a programming error to call this when the `type` is not a group.
+ */
+@property(nonatomic, readonly, strong, nonnull) GPBUnknownFields *group;
+
+/**
+ * An array of varint values for this field.
+ *
+ * Only valid for type == GPBUnknownFieldTypeLegacy, it is a programming error
+ * to use with any other type.
+ */
 @property(nonatomic, readonly, strong) GPBUInt64Array *varintList;
 
-/** An array of fixed32 values for this field. */
+/**
+ * An array of fixed32 values for this field.
+ *
+ * Only valid for type == GPBUnknownFieldTypeLegacy, it is a programming error
+ * to use with any other type.
+ */
 @property(nonatomic, readonly, strong) GPBUInt32Array *fixed32List;
 
-/** An array of fixed64 values for this field. */
+/**
+ * An array of fixed64 values for this field.
+ *
+ * Only valid for type == GPBUnknownFieldTypeLegacy, it is a programming error
+ * to use with any other type.
+ */
 @property(nonatomic, readonly, strong) GPBUInt64Array *fixed64List;
 
-/** An array of data values for this field. */
+/**
+ * An array of data values for this field.
+ *
+ * Only valid for type == GPBUnknownFieldTypeLegacy, it is a programming error
+ * to use with any other type.
+ */
 @property(nonatomic, readonly, strong) NSArray<NSData *> *lengthDelimitedList;
 
-/** An array of groups of values for this field. */
+/**
+ * An array of groups of values for this field.
+ *
+ * Only valid for type == GPBUnknownFieldTypeLegacy, it is a programming error
+ * to use with any other type.
+ */
 @property(nonatomic, readonly, strong) NSArray<GPBUnknownFieldSet *> *groupList;
 
 /**
  * Add a value to the varintList.
  *
+ * Only valid for type == GPBUnknownFieldTypeLegacy, it is a programming error
+ * to use with any other type.
+ *
  * @param value The value to add.
  **/
 - (void)addVarint:(uint64_t)value;
 /**
  * Add a value to the fixed32List.
  *
+ * Only valid for type == GPBUnknownFieldTypeLegacy, it is a programming error
+ * to use with any other type.
+ *
  * @param value The value to add.
  **/
 - (void)addFixed32:(uint32_t)value;
 /**
  * Add a value to the fixed64List.
  *
+ * Only valid for type == GPBUnknownFieldTypeLegacy, it is a programming error
+ * to use with any other type.
+ *
  * @param value The value to add.
  **/
 - (void)addFixed64:(uint64_t)value;
 /**
  * Add a value to the lengthDelimitedList.
  *
+ * Only valid for type == GPBUnknownFieldTypeLegacy, it is a programming error
+ * to use with any other type.
+ *
  * @param value The value to add.
  **/
 - (void)addLengthDelimited:(NSData *)value;
 /**
  * Add a value to the groupList.
  *
+ * Only valid for type == GPBUnknownFieldTypeLegacy, it is a programming error
+ * to use with any other type.
+ *
  * @param value The value to add.
  **/
 - (void)addGroup:(GPBUnknownFieldSet *)value;
diff --git a/objectivec/GPBUnknownField.m b/objectivec/GPBUnknownField.m
index 69f834f..767bc5b 100644
--- a/objectivec/GPBUnknownField.m
+++ b/objectivec/GPBUnknownField.m
@@ -5,42 +5,114 @@
 // license that can be found in the LICENSE file or at
 // https://developers.google.com/open-source/licenses/bsd
 
+#import "GPBUnknownField.h"
 #import "GPBUnknownField_PackagePrivate.h"
 
 #import "GPBArray.h"
 #import "GPBCodedOutputStream_PackagePrivate.h"
 #import "GPBUnknownFieldSet.h"
 
+#define ASSERT_FIELD_TYPE(type)                               \
+  if (type_ != type) {                                        \
+    [NSException raise:NSInternalInconsistencyException       \
+                format:@"GPBUnknownField is the wrong type"]; \
+  }
+
 @implementation GPBUnknownField {
  @protected
   int32_t number_;
-  GPBUInt64Array *mutableVarintList_;
-  GPBUInt32Array *mutableFixed32List_;
-  GPBUInt64Array *mutableFixed64List_;
-  NSMutableArray<NSData *> *mutableLengthDelimitedList_;
-  NSMutableArray<GPBUnknownFieldSet *> *mutableGroupList_;
+  GPBUnknownFieldType type_;
+
+  union {
+    uint64_t intValue;        // type == Varint, Fixed32, Fixed64
+    NSData *lengthDelimited;  // type == LengthDelimited
+    GPBUnknownFields *group;  // type == Group
+    struct {                  // type == Legacy
+      GPBUInt64Array *mutableVarintList;
+      GPBUInt32Array *mutableFixed32List;
+      GPBUInt64Array *mutableFixed64List;
+      NSMutableArray<NSData *> *mutableLengthDelimitedList;
+      NSMutableArray<GPBUnknownFieldSet *> *mutableGroupList;
+    } legacy;
+  } storage_;
 }
 
 @synthesize number = number_;
-@synthesize varintList = mutableVarintList_;
-@synthesize fixed32List = mutableFixed32List_;
-@synthesize fixed64List = mutableFixed64List_;
-@synthesize lengthDelimitedList = mutableLengthDelimitedList_;
-@synthesize groupList = mutableGroupList_;
+@synthesize type = type_;
 
 - (instancetype)initWithNumber:(int32_t)number {
   if ((self = [super init])) {
     number_ = number;
+    type_ = GPBUnknownFieldTypeLegacy;
+  }
+  return self;
+}
+
+- (instancetype)initWithNumber:(int32_t)number varint:(uint64_t)varint {
+  if ((self = [super init])) {
+    number_ = number;
+    type_ = GPBUnknownFieldTypeVarint;
+    storage_.intValue = varint;
+  }
+  return self;
+}
+
+- (instancetype)initWithNumber:(int32_t)number fixed32:(uint32_t)fixed32 {
+  if ((self = [super init])) {
+    number_ = number;
+    type_ = GPBUnknownFieldTypeFixed32;
+    storage_.intValue = fixed32;
+  }
+  return self;
+}
+
+- (instancetype)initWithNumber:(int32_t)number fixed64:(uint64_t)fixed64 {
+  if ((self = [super init])) {
+    number_ = number;
+    type_ = GPBUnknownFieldTypeFixed64;
+    storage_.intValue = fixed64;
+  }
+  return self;
+}
+
+- (instancetype)initWithNumber:(int32_t)number lengthDelimited:(nonnull NSData *)data {
+  if ((self = [super init])) {
+    number_ = number;
+    type_ = GPBUnknownFieldTypeLengthDelimited;
+    storage_.lengthDelimited = [data copy];
+  }
+  return self;
+}
+
+- (instancetype)initWithNumber:(int32_t)number group:(nonnull GPBUnknownFields *)group {
+  if ((self = [super init])) {
+    number_ = number;
+    type_ = GPBUnknownFieldTypeGroup;
+    storage_.group = [group retain];
   }
   return self;
 }
 
 - (void)dealloc {
-  [mutableVarintList_ release];
-  [mutableFixed32List_ release];
-  [mutableFixed64List_ release];
-  [mutableLengthDelimitedList_ release];
-  [mutableGroupList_ release];
+  switch (type_) {
+    case GPBUnknownFieldTypeVarint:
+    case GPBUnknownFieldTypeFixed32:
+    case GPBUnknownFieldTypeFixed64:
+      break;
+    case GPBUnknownFieldTypeLengthDelimited:
+      [storage_.lengthDelimited release];
+      break;
+    case GPBUnknownFieldTypeGroup:
+      [storage_.group release];
+      break;
+    case GPBUnknownFieldTypeLegacy:
+      [storage_.legacy.mutableVarintList release];
+      [storage_.legacy.mutableFixed32List release];
+      [storage_.legacy.mutableFixed64List release];
+      [storage_.legacy.mutableLengthDelimitedList release];
+      [storage_.legacy.mutableGroupList release];
+      break;
+  }
 
   [super dealloc];
 }
@@ -51,22 +123,96 @@
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wdirect-ivar-access"
 
+- (uint64_t)varint {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeVarint);
+  return storage_.intValue;
+}
+
+- (uint32_t)fixed32 {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeFixed32);
+  return (uint32_t)storage_.intValue;
+}
+
+- (uint64_t)fixed64 {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeFixed64);
+  return storage_.intValue;
+}
+
+- (NSData *)lengthDelimited {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLengthDelimited);
+  return storage_.lengthDelimited;
+}
+
+- (GPBUnknownFields *)group {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeGroup);
+  return storage_.group;
+}
+
+- (GPBUInt64Array *)varintList {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
+  return storage_.legacy.mutableVarintList;
+}
+
+- (GPBUInt32Array *)fixed32List {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
+  return storage_.legacy.mutableFixed32List;
+}
+
+- (GPBUInt64Array *)fixed64List {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
+  return storage_.legacy.mutableFixed64List;
+}
+
+- (NSArray<NSData *> *)lengthDelimitedList {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
+  return storage_.legacy.mutableLengthDelimitedList;
+}
+
+- (NSArray<GPBUnknownFieldSet *> *)groupList {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
+  return storage_.legacy.mutableGroupList;
+}
+
 - (id)copyWithZone:(NSZone *)zone {
-  GPBUnknownField *result = [[GPBUnknownField allocWithZone:zone] initWithNumber:number_];
-  result->mutableFixed32List_ = [mutableFixed32List_ copyWithZone:zone];
-  result->mutableFixed64List_ = [mutableFixed64List_ copyWithZone:zone];
-  result->mutableLengthDelimitedList_ = [mutableLengthDelimitedList_ mutableCopyWithZone:zone];
-  result->mutableVarintList_ = [mutableVarintList_ copyWithZone:zone];
-  if (mutableGroupList_.count) {
-    result->mutableGroupList_ =
-        [[NSMutableArray allocWithZone:zone] initWithCapacity:mutableGroupList_.count];
-    for (GPBUnknownFieldSet *group in mutableGroupList_) {
-      GPBUnknownFieldSet *copied = [group copyWithZone:zone];
-      [result->mutableGroupList_ addObject:copied];
-      [copied release];
+  switch (type_) {
+    case GPBUnknownFieldTypeVarint:
+      return [[GPBUnknownField allocWithZone:zone] initWithNumber:number_ varint:storage_.intValue];
+    case GPBUnknownFieldTypeFixed32:
+      return [[GPBUnknownField allocWithZone:zone] initWithNumber:number_
+                                                          fixed32:(uint32_t)storage_.intValue];
+    case GPBUnknownFieldTypeFixed64:
+      return [[GPBUnknownField allocWithZone:zone] initWithNumber:number_
+                                                          fixed64:storage_.intValue];
+    case GPBUnknownFieldTypeLengthDelimited:
+      return [[GPBUnknownField allocWithZone:zone]
+           initWithNumber:number_
+          lengthDelimited:[storage_.lengthDelimited copyWithZone:zone]];
+    case GPBUnknownFieldTypeGroup:
+      return
+          [[GPBUnknownField allocWithZone:zone] initWithNumber:number_
+                                                         group:[storage_.group copyWithZone:zone]];
+    case GPBUnknownFieldTypeLegacy: {
+      GPBUnknownField *result = [[GPBUnknownField allocWithZone:zone] initWithNumber:number_];
+      result->storage_.legacy.mutableFixed32List =
+          [storage_.legacy.mutableFixed32List copyWithZone:zone];
+      result->storage_.legacy.mutableFixed64List =
+          [storage_.legacy.mutableFixed64List copyWithZone:zone];
+      result->storage_.legacy.mutableLengthDelimitedList =
+          [storage_.legacy.mutableLengthDelimitedList mutableCopyWithZone:zone];
+      result->storage_.legacy.mutableVarintList =
+          [storage_.legacy.mutableVarintList copyWithZone:zone];
+      if (storage_.legacy.mutableGroupList.count) {
+        result->storage_.legacy.mutableGroupList = [[NSMutableArray allocWithZone:zone]
+            initWithCapacity:storage_.legacy.mutableGroupList.count];
+        for (GPBUnknownFieldSet *group in storage_.legacy.mutableGroupList) {
+          GPBUnknownFieldSet *copied = [group copyWithZone:zone];
+          [result->storage_.legacy.mutableGroupList addObject:copied];
+          [copied release];
+        }
+      }
+      return result;
     }
   }
-  return result;
 }
 
 - (BOOL)isEqual:(id)object {
@@ -74,82 +220,120 @@
   if (![object isKindOfClass:[GPBUnknownField class]]) return NO;
   GPBUnknownField *field = (GPBUnknownField *)object;
   if (number_ != field->number_) return NO;
-  BOOL equalVarint = (mutableVarintList_.count == 0 && field->mutableVarintList_.count == 0) ||
-                     [mutableVarintList_ isEqual:field->mutableVarintList_];
-  if (!equalVarint) return NO;
-  BOOL equalFixed32 = (mutableFixed32List_.count == 0 && field->mutableFixed32List_.count == 0) ||
-                      [mutableFixed32List_ isEqual:field->mutableFixed32List_];
-  if (!equalFixed32) return NO;
-  BOOL equalFixed64 = (mutableFixed64List_.count == 0 && field->mutableFixed64List_.count == 0) ||
-                      [mutableFixed64List_ isEqual:field->mutableFixed64List_];
-  if (!equalFixed64) return NO;
-  BOOL equalLDList =
-      (mutableLengthDelimitedList_.count == 0 && field->mutableLengthDelimitedList_.count == 0) ||
-      [mutableLengthDelimitedList_ isEqual:field->mutableLengthDelimitedList_];
-  if (!equalLDList) return NO;
-  BOOL equalGroupList = (mutableGroupList_.count == 0 && field->mutableGroupList_.count == 0) ||
-                        [mutableGroupList_ isEqual:field->mutableGroupList_];
-  if (!equalGroupList) return NO;
-  return YES;
+  if (type_ != field->type_) return NO;
+  switch (type_) {
+    case GPBUnknownFieldTypeVarint:
+    case GPBUnknownFieldTypeFixed32:
+    case GPBUnknownFieldTypeFixed64:
+      return storage_.intValue == field->storage_.intValue;
+    case GPBUnknownFieldTypeLengthDelimited:
+      return [storage_.lengthDelimited isEqual:field->storage_.lengthDelimited];
+    case GPBUnknownFieldTypeGroup:
+      return [storage_.group isEqual:field->storage_.group];
+    case GPBUnknownFieldTypeLegacy: {
+      BOOL equalVarint =
+          (storage_.legacy.mutableVarintList.count == 0 &&
+           field->storage_.legacy.mutableVarintList.count == 0) ||
+          [storage_.legacy.mutableVarintList isEqual:field->storage_.legacy.mutableVarintList];
+      if (!equalVarint) return NO;
+      BOOL equalFixed32 =
+          (storage_.legacy.mutableFixed32List.count == 0 &&
+           field->storage_.legacy.mutableFixed32List.count == 0) ||
+          [storage_.legacy.mutableFixed32List isEqual:field->storage_.legacy.mutableFixed32List];
+      if (!equalFixed32) return NO;
+      BOOL equalFixed64 =
+          (storage_.legacy.mutableFixed64List.count == 0 &&
+           field->storage_.legacy.mutableFixed64List.count == 0) ||
+          [storage_.legacy.mutableFixed64List isEqual:field->storage_.legacy.mutableFixed64List];
+      if (!equalFixed64) return NO;
+      BOOL equalLDList = (storage_.legacy.mutableLengthDelimitedList.count == 0 &&
+                          field->storage_.legacy.mutableLengthDelimitedList.count == 0) ||
+                         [storage_.legacy.mutableLengthDelimitedList
+                             isEqual:field->storage_.legacy.mutableLengthDelimitedList];
+      if (!equalLDList) return NO;
+      BOOL equalGroupList =
+          (storage_.legacy.mutableGroupList.count == 0 &&
+           field->storage_.legacy.mutableGroupList.count == 0) ||
+          [storage_.legacy.mutableGroupList isEqual:field->storage_.legacy.mutableGroupList];
+      if (!equalGroupList) return NO;
+      return YES;
+    }
+  }
 }
 
 - (NSUInteger)hash {
-  // Just mix the hashes of the possible sub arrays.
   const int prime = 31;
-  NSUInteger result = prime + [mutableVarintList_ hash];
-  result = prime * result + [mutableFixed32List_ hash];
-  result = prime * result + [mutableFixed64List_ hash];
-  result = prime * result + [mutableLengthDelimitedList_ hash];
-  result = prime * result + [mutableGroupList_ hash];
+  NSUInteger result = prime * number_ + type_;
+  switch (type_) {
+    case GPBUnknownFieldTypeVarint:
+    case GPBUnknownFieldTypeFixed32:
+    case GPBUnknownFieldTypeFixed64:
+      result = prime * result + (NSUInteger)storage_.intValue;
+      break;
+    case GPBUnknownFieldTypeLengthDelimited:
+      result = prime * result + [storage_.lengthDelimited hash];
+      break;
+    case GPBUnknownFieldTypeGroup:
+      result = prime * result + [storage_.group hash];
+    case GPBUnknownFieldTypeLegacy:
+      result = prime * result + [storage_.legacy.mutableVarintList hash];
+      result = prime * result + [storage_.legacy.mutableFixed32List hash];
+      result = prime * result + [storage_.legacy.mutableFixed64List hash];
+      result = prime * result + [storage_.legacy.mutableLengthDelimitedList hash];
+      result = prime * result + [storage_.legacy.mutableGroupList hash];
+      break;
+  }
   return result;
 }
 
 - (void)writeToOutput:(GPBCodedOutputStream *)output {
-  NSUInteger count = mutableVarintList_.count;
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
+  NSUInteger count = storage_.legacy.mutableVarintList.count;
   if (count > 0) {
-    [output writeUInt64Array:number_ values:mutableVarintList_ tag:0];
+    [output writeUInt64Array:number_ values:storage_.legacy.mutableVarintList tag:0];
   }
-  count = mutableFixed32List_.count;
+  count = storage_.legacy.mutableFixed32List.count;
   if (count > 0) {
-    [output writeFixed32Array:number_ values:mutableFixed32List_ tag:0];
+    [output writeFixed32Array:number_ values:storage_.legacy.mutableFixed32List tag:0];
   }
-  count = mutableFixed64List_.count;
+  count = storage_.legacy.mutableFixed64List.count;
   if (count > 0) {
-    [output writeFixed64Array:number_ values:mutableFixed64List_ tag:0];
+    [output writeFixed64Array:number_ values:storage_.legacy.mutableFixed64List tag:0];
   }
-  count = mutableLengthDelimitedList_.count;
+  count = storage_.legacy.mutableLengthDelimitedList.count;
   if (count > 0) {
-    [output writeBytesArray:number_ values:mutableLengthDelimitedList_];
+    [output writeBytesArray:number_ values:storage_.legacy.mutableLengthDelimitedList];
   }
-  count = mutableGroupList_.count;
+  count = storage_.legacy.mutableGroupList.count;
   if (count > 0) {
-    [output writeUnknownGroupArray:number_ values:mutableGroupList_];
+    [output writeUnknownGroupArray:number_ values:storage_.legacy.mutableGroupList];
   }
 }
 
 - (size_t)serializedSize {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
   __block size_t result = 0;
   int32_t number = number_;
-  [mutableVarintList_
+  [storage_.legacy.mutableVarintList
       enumerateValuesWithBlock:^(uint64_t value, __unused NSUInteger idx, __unused BOOL *stop) {
         result += GPBComputeUInt64Size(number, value);
       }];
 
-  [mutableFixed32List_
+  [storage_.legacy.mutableFixed32List
       enumerateValuesWithBlock:^(uint32_t value, __unused NSUInteger idx, __unused BOOL *stop) {
         result += GPBComputeFixed32Size(number, value);
       }];
 
-  [mutableFixed64List_
+  [storage_.legacy.mutableFixed64List
       enumerateValuesWithBlock:^(uint64_t value, __unused NSUInteger idx, __unused BOOL *stop) {
         result += GPBComputeFixed64Size(number, value);
       }];
 
-  for (NSData *data in mutableLengthDelimitedList_) {
+  for (NSData *data in storage_.legacy.mutableLengthDelimitedList) {
     result += GPBComputeBytesSize(number, data);
   }
 
-  for (GPBUnknownFieldSet *set in mutableGroupList_) {
+  for (GPBUnknownFieldSet *set in storage_.legacy.mutableGroupList) {
     result += GPBComputeUnknownGroupSize(number, set);
   }
 
@@ -157,14 +341,16 @@
 }
 
 - (void)writeAsMessageSetExtensionToOutput:(GPBCodedOutputStream *)output {
-  for (NSData *data in mutableLengthDelimitedList_) {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
+  for (NSData *data in storage_.legacy.mutableLengthDelimitedList) {
     [output writeRawMessageSetExtension:number_ value:data];
   }
 }
 
 - (size_t)serializedSizeAsMessageSetExtension {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
   size_t result = 0;
-  for (NSData *data in mutableLengthDelimitedList_) {
+  for (NSData *data in storage_.legacy.mutableLengthDelimitedList) {
     result += GPBComputeRawMessageSetExtensionSize(number_, data);
   }
   return result;
@@ -172,121 +358,145 @@
 
 - (NSString *)description {
   NSMutableString *description =
-      [NSMutableString stringWithFormat:@"<%@ %p>: Field: %d {\n", [self class], self, number_];
-  [mutableVarintList_
-      enumerateValuesWithBlock:^(uint64_t value, __unused NSUInteger idx, __unused BOOL *stop) {
-        [description appendFormat:@"\t%llu\n", value];
-      }];
-
-  [mutableFixed32List_
-      enumerateValuesWithBlock:^(uint32_t value, __unused NSUInteger idx, __unused BOOL *stop) {
-        [description appendFormat:@"\t%u\n", value];
-      }];
-
-  [mutableFixed64List_
-      enumerateValuesWithBlock:^(uint64_t value, __unused NSUInteger idx, __unused BOOL *stop) {
-        [description appendFormat:@"\t%llu\n", value];
-      }];
-
-  for (NSData *data in mutableLengthDelimitedList_) {
-    [description appendFormat:@"\t%@\n", data];
+      [NSMutableString stringWithFormat:@"<%@ %p>: Field: %d", [self class], self, number_];
+  switch (type_) {
+    case GPBUnknownFieldTypeVarint:
+      [description appendFormat:@" varint: %llu", storage_.intValue];
+      break;
+    case GPBUnknownFieldTypeFixed32:
+      [description appendFormat:@" fixed32: %u", (uint32_t)storage_.intValue];
+      break;
+    case GPBUnknownFieldTypeFixed64:
+      [description appendFormat:@" fixed64: %llu", storage_.intValue];
+      break;
+    case GPBUnknownFieldTypeLengthDelimited:
+      [description appendFormat:@" fixed64: %@", storage_.lengthDelimited];
+      break;
+    case GPBUnknownFieldTypeGroup:
+      [description appendFormat:@" group: %@", storage_.group];
+      break;
+    case GPBUnknownFieldTypeLegacy:
+      [description appendString:@" {\n"];
+      [storage_.legacy.mutableVarintList
+          enumerateValuesWithBlock:^(uint64_t value, __unused NSUInteger idx, __unused BOOL *stop) {
+            [description appendFormat:@"\t%llu\n", value];
+          }];
+      [storage_.legacy.mutableFixed32List
+          enumerateValuesWithBlock:^(uint32_t value, __unused NSUInteger idx, __unused BOOL *stop) {
+            [description appendFormat:@"\t%u\n", value];
+          }];
+      [storage_.legacy.mutableFixed64List
+          enumerateValuesWithBlock:^(uint64_t value, __unused NSUInteger idx, __unused BOOL *stop) {
+            [description appendFormat:@"\t%llu\n", value];
+          }];
+      for (NSData *data in storage_.legacy.mutableLengthDelimitedList) {
+        [description appendFormat:@"\t%@\n", data];
+      }
+      for (GPBUnknownFieldSet *set in storage_.legacy.mutableGroupList) {
+        [description appendFormat:@"\t%@\n", set];
+      }
+      [description appendString:@"}"];
+      break;
   }
-
-  for (GPBUnknownFieldSet *set in mutableGroupList_) {
-    [description appendFormat:@"\t%@\n", set];
-  }
-  [description appendString:@"}"];
   return description;
 }
 
 - (void)mergeFromField:(GPBUnknownField *)other {
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
   GPBUInt64Array *otherVarintList = other.varintList;
   if (otherVarintList.count > 0) {
-    if (mutableVarintList_ == nil) {
-      mutableVarintList_ = [otherVarintList copy];
+    if (storage_.legacy.mutableVarintList == nil) {
+      storage_.legacy.mutableVarintList = [otherVarintList copy];
     } else {
-      [mutableVarintList_ addValuesFromArray:otherVarintList];
+      [storage_.legacy.mutableVarintList addValuesFromArray:otherVarintList];
     }
   }
 
   GPBUInt32Array *otherFixed32List = other.fixed32List;
   if (otherFixed32List.count > 0) {
-    if (mutableFixed32List_ == nil) {
-      mutableFixed32List_ = [otherFixed32List copy];
+    if (storage_.legacy.mutableFixed32List == nil) {
+      storage_.legacy.mutableFixed32List = [otherFixed32List copy];
     } else {
-      [mutableFixed32List_ addValuesFromArray:otherFixed32List];
+      [storage_.legacy.mutableFixed32List addValuesFromArray:otherFixed32List];
     }
   }
 
   GPBUInt64Array *otherFixed64List = other.fixed64List;
   if (otherFixed64List.count > 0) {
-    if (mutableFixed64List_ == nil) {
-      mutableFixed64List_ = [otherFixed64List copy];
+    if (storage_.legacy.mutableFixed64List == nil) {
+      storage_.legacy.mutableFixed64List = [otherFixed64List copy];
     } else {
-      [mutableFixed64List_ addValuesFromArray:otherFixed64List];
+      [storage_.legacy.mutableFixed64List addValuesFromArray:otherFixed64List];
     }
   }
 
   NSArray *otherLengthDelimitedList = other.lengthDelimitedList;
   if (otherLengthDelimitedList.count > 0) {
-    if (mutableLengthDelimitedList_ == nil) {
-      mutableLengthDelimitedList_ = [otherLengthDelimitedList mutableCopy];
+    if (storage_.legacy.mutableLengthDelimitedList == nil) {
+      storage_.legacy.mutableLengthDelimitedList = [otherLengthDelimitedList mutableCopy];
     } else {
-      [mutableLengthDelimitedList_ addObjectsFromArray:otherLengthDelimitedList];
+      [storage_.legacy.mutableLengthDelimitedList addObjectsFromArray:otherLengthDelimitedList];
     }
   }
 
   NSArray *otherGroupList = other.groupList;
   if (otherGroupList.count > 0) {
-    if (mutableGroupList_ == nil) {
-      mutableGroupList_ = [[NSMutableArray alloc] initWithCapacity:otherGroupList.count];
+    if (storage_.legacy.mutableGroupList == nil) {
+      storage_.legacy.mutableGroupList =
+          [[NSMutableArray alloc] initWithCapacity:otherGroupList.count];
     }
     // Make our own mutable copies.
     for (GPBUnknownFieldSet *group in otherGroupList) {
       GPBUnknownFieldSet *copied = [group copy];
-      [mutableGroupList_ addObject:copied];
+      [storage_.legacy.mutableGroupList addObject:copied];
       [copied release];
     }
   }
 }
 
 - (void)addVarint:(uint64_t)value {
-  if (mutableVarintList_ == nil) {
-    mutableVarintList_ = [[GPBUInt64Array alloc] initWithValues:&value count:1];
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
+  if (storage_.legacy.mutableVarintList == nil) {
+    storage_.legacy.mutableVarintList = [[GPBUInt64Array alloc] initWithValues:&value count:1];
   } else {
-    [mutableVarintList_ addValue:value];
+    [storage_.legacy.mutableVarintList addValue:value];
   }
 }
 
 - (void)addFixed32:(uint32_t)value {
-  if (mutableFixed32List_ == nil) {
-    mutableFixed32List_ = [[GPBUInt32Array alloc] initWithValues:&value count:1];
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
+  if (storage_.legacy.mutableFixed32List == nil) {
+    storage_.legacy.mutableFixed32List = [[GPBUInt32Array alloc] initWithValues:&value count:1];
   } else {
-    [mutableFixed32List_ addValue:value];
+    [storage_.legacy.mutableFixed32List addValue:value];
   }
 }
 
 - (void)addFixed64:(uint64_t)value {
-  if (mutableFixed64List_ == nil) {
-    mutableFixed64List_ = [[GPBUInt64Array alloc] initWithValues:&value count:1];
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
+  if (storage_.legacy.mutableFixed64List == nil) {
+    storage_.legacy.mutableFixed64List = [[GPBUInt64Array alloc] initWithValues:&value count:1];
   } else {
-    [mutableFixed64List_ addValue:value];
+    [storage_.legacy.mutableFixed64List addValue:value];
   }
 }
 
 - (void)addLengthDelimited:(NSData *)value {
-  if (mutableLengthDelimitedList_ == nil) {
-    mutableLengthDelimitedList_ = [[NSMutableArray alloc] initWithObjects:&value count:1];
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
+  if (storage_.legacy.mutableLengthDelimitedList == nil) {
+    storage_.legacy.mutableLengthDelimitedList = [[NSMutableArray alloc] initWithObjects:&value
+                                                                                   count:1];
   } else {
-    [mutableLengthDelimitedList_ addObject:value];
+    [storage_.legacy.mutableLengthDelimitedList addObject:value];
   }
 }
 
 - (void)addGroup:(GPBUnknownFieldSet *)value {
-  if (mutableGroupList_ == nil) {
-    mutableGroupList_ = [[NSMutableArray alloc] initWithObjects:&value count:1];
+  ASSERT_FIELD_TYPE(GPBUnknownFieldTypeLegacy);
+  if (storage_.legacy.mutableGroupList == nil) {
+    storage_.legacy.mutableGroupList = [[NSMutableArray alloc] initWithObjects:&value count:1];
   } else {
-    [mutableGroupList_ addObject:value];
+    [storage_.legacy.mutableGroupList addObject:value];
   }
 }
 
diff --git a/objectivec/GPBUnknownField_PackagePrivate.h b/objectivec/GPBUnknownField_PackagePrivate.h
index 17304f3..e95358f 100644
--- a/objectivec/GPBUnknownField_PackagePrivate.h
+++ b/objectivec/GPBUnknownField_PackagePrivate.h
@@ -13,12 +13,18 @@
 
 @interface GPBUnknownField ()
 
-- (void)writeToOutput:(GPBCodedOutputStream *)output;
+- (nonnull instancetype)initWithNumber:(int32_t)number varint:(uint64_t)varint;
+- (nonnull instancetype)initWithNumber:(int32_t)number fixed32:(uint32_t)fixed32;
+- (nonnull instancetype)initWithNumber:(int32_t)number fixed64:(uint64_t)fixed64;
+- (nonnull instancetype)initWithNumber:(int32_t)number lengthDelimited:(nonnull NSData *)data;
+- (nonnull instancetype)initWithNumber:(int32_t)number group:(nonnull GPBUnknownFields *)group;
+
+- (void)writeToOutput:(nonnull GPBCodedOutputStream *)output;
 - (size_t)serializedSize;
 
-- (void)writeAsMessageSetExtensionToOutput:(GPBCodedOutputStream *)output;
+- (void)writeAsMessageSetExtensionToOutput:(nonnull GPBCodedOutputStream *)output;
 - (size_t)serializedSizeAsMessageSetExtension;
 
-- (void)mergeFromField:(GPBUnknownField *)other;
+- (void)mergeFromField:(nonnull GPBUnknownField *)other;
 
 @end
diff --git a/objectivec/GPBUnknownFields.h b/objectivec/GPBUnknownFields.h
new file mode 100644
index 0000000..07c4dbf
--- /dev/null
+++ b/objectivec/GPBUnknownFields.h
@@ -0,0 +1,155 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2024 Google Inc.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#import <Foundation/Foundation.h>
+
+@class GPBUnknownField;
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * A collection of unknown field numbers and their values.
+ *
+ * Note: `NSFastEnumeration` is supported to iterate over the `GPBUnknownFields`
+ * in order.
+ *
+ * Reminder: Any field number can occur multiple times. For example, if a .proto
+ * file were updated to a have a new (unpacked) repeated field, then each value
+ * would appear independently. Likewise, it is possible that a number appears
+ * multiple times with different data types, i.e. - unpacked vs. package repeated
+ * fields from concatenating binary blobs of data.
+ */
+__attribute__((objc_subclassing_restricted))
+@interface GPBUnknownFields : NSObject<NSCopying, NSFastEnumeration>
+
+/**
+ * Initializes a new empty instance.
+ **/
+- (instancetype)init;
+
+/**
+ * The number of fields in this set. A single field number can appear in
+ * multiple `GPBUnknownField` values as it might be a repeated field (it is
+ * also possible that they have different `type` values (for example package vs
+ * unpacked repeated fields).
+ *
+ * Note: `NSFastEnumeration` is supported to iterate over the fields in order.
+ **/
+@property(nonatomic, readonly, assign) NSUInteger count;
+
+/** If the set is empty or not. */
+@property(nonatomic, readonly, assign) BOOL empty;
+
+/**
+ * Removes all the fields current in the set.
+ **/
+- (void)clear;
+
+/**
+ * Fetches the subset of all the unknown fields that are for the given field
+ * number.
+ *
+ * @returns An `NSArray` of `GPBUnknownField`s or `nil` if there were none.
+ */
+- (nullable NSArray<GPBUnknownField *> *)fields:(int32_t)fieldNumber;
+
+/**
+ * Add a new varint unknown field.
+ *
+ * @param fieldNumber The field number to use.
+ * @param value The value to add.
+ **/
+- (void)addFieldNumber:(int32_t)fieldNumber varint:(uint64_t)value;
+
+/**
+ * Add a new fixed32 unknown field.
+ *
+ * @param fieldNumber The field number to use.
+ * @param value The value to add.
+ **/
+- (void)addFieldNumber:(int32_t)fieldNumber fixed32:(uint32_t)value;
+
+/**
+ * Add a new fixed64 unknown field.
+ *
+ * @param fieldNumber The field number to use.
+ * @param value The value to add.
+ **/
+- (void)addFieldNumber:(int32_t)fieldNumber fixed64:(uint64_t)value;
+
+/**
+ * Add a new length delimited (length prefixed) unknown field.
+ *
+ * @param fieldNumber The field number to use.
+ * @param value The value to add.
+ **/
+- (void)addFieldNumber:(int32_t)fieldNumber lengthDelimited:(nonnull NSData *)value;
+
+/**
+ * Add a group (tag delimited) unknown field.
+ *
+ * @param fieldNumber The field number to use.
+ *
+ * @return A new `GPBUnknownFields` to set the field of the group too.
+ **/
+- (nonnull GPBUnknownFields *)addGroupWithFieldNumber:(int32_t)fieldNumber;
+
+@end
+
+@interface GPBUnknownFields (AccessHelpers)
+
+/**
+ * Fetches the first varint for the given field number.
+ *
+ * @param fieldNumber The field number to look for.
+ * @param outValue A pointer to receive the value if found
+ *
+ * @returns YES/NO on if there was a matching unknown field.
+ **/
+- (BOOL)getFirst:(int32_t)fieldNumber varint:(nonnull uint64_t *)outValue;
+
+/**
+ * Fetches the first fixed32 for the given field number.
+ *
+ * @param fieldNumber The field number to look for.
+ * @param outValue A pointer to receive the value if found
+ *
+ * @returns YES/NO on if there was a matching unknown field.
+ **/
+- (BOOL)getFirst:(int32_t)fieldNumber fixed32:(nonnull uint32_t *)outValue;
+
+/**
+ * Fetches the first fixed64 for the given field number.
+ *
+ * @param fieldNumber The field number to look for.
+ * @param outValue A pointer to receive the value if found
+ *
+ * @returns YES/NO on if there was a matching unknown field.
+ **/
+- (BOOL)getFirst:(int32_t)fieldNumber fixed64:(nonnull uint64_t *)outValue;
+
+/**
+ * Fetches the first length delimited (length prefixed) for the given field number.
+ *
+ * @param fieldNumber The field number to look for.
+ *
+ * @returns The first length delimited value for the given field number.
+ **/
+- (nullable NSData *)firstLengthDelimited:(int32_t)fieldNumber;
+
+/**
+ * Fetches the first group (tag delimited) field for the given field number.
+ *
+ * @param fieldNumber The field number to look for.
+ *
+ * @returns The first group for the given field number.
+ **/
+- (nullable GPBUnknownFields *)firstGroup:(int32_t)fieldNumber;
+
+@end
+
+NS_ASSUME_NONNULL_END
diff --git a/objectivec/GPBUnknownFields.m b/objectivec/GPBUnknownFields.m
new file mode 100644
index 0000000..aed1bc9
--- /dev/null
+++ b/objectivec/GPBUnknownFields.m
@@ -0,0 +1,199 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2024 Google Inc.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#import "GPBUnknownFields.h"
+#import "GPBUnknownField_PackagePrivate.h"
+
+#define CHECK_FIELD_NUMBER(number)                                                      \
+  if (number <= 0) {                                                                    \
+    [NSException raise:NSInvalidArgumentException format:@"Not a valid field number."]; \
+  }
+
+@implementation GPBUnknownFields {
+ @package
+  NSMutableArray<GPBUnknownField *> *fields_;
+}
+
+// Direct access is use for speed, to avoid even internally declaring things
+// read/write, etc. The warning is enabled in the project to ensure code calling
+// protos can turn on -Wdirect-ivar-access without issues.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdirect-ivar-access"
+
+- (instancetype)init {
+  self = [super init];
+  if (self) {
+    fields_ = [[NSMutableArray alloc] init];
+  }
+  return self;
+}
+
+- (id)copyWithZone:(NSZone *)zone {
+  GPBUnknownFields *copy = [[GPBUnknownFields alloc] init];
+  // Fields are r/o in this api, so just copy the array.
+  copy->fields_ = [fields_ mutableCopyWithZone:zone];
+  return copy;
+}
+
+- (void)dealloc {
+  [fields_ release];
+  [super dealloc];
+}
+
+- (BOOL)isEqual:(id)object {
+  if (![object isKindOfClass:[GPBUnknownFields class]]) {
+    return NO;
+  }
+  GPBUnknownFields *ufs = (GPBUnknownFields *)object;
+  // The type is defined with order of fields mattering, so just compare the arrays.
+  return [fields_ isEqual:ufs->fields_];
+}
+
+- (NSUInteger)hash {
+  return [fields_ hash];
+}
+
+- (NSString *)description {
+  return [NSString
+      stringWithFormat:@"<%@ %p>: %lu fields", [self class], self, (unsigned long)fields_.count];
+}
+
+#pragma mark - Public Methods
+
+- (NSUInteger)count {
+  return fields_.count;
+}
+
+- (BOOL)empty {
+  return fields_.count == 0;
+}
+
+- (void)clear {
+  [fields_ removeAllObjects];
+}
+
+- (NSArray<GPBUnknownField *> *)fields:(int32_t)fieldNumber {
+  CHECK_FIELD_NUMBER(fieldNumber);
+  NSMutableArray<GPBUnknownField *> *result = [[NSMutableArray alloc] init];
+  for (GPBUnknownField *field in fields_) {
+    if (field.number == fieldNumber) {
+      [result addObject:field];
+    }
+  }
+  if (result.count == 0) {
+    [result release];
+    return nil;
+  }
+  return [result autorelease];
+}
+
+- (void)addFieldNumber:(int32_t)fieldNumber varint:(uint64_t)value {
+  CHECK_FIELD_NUMBER(fieldNumber);
+  GPBUnknownField *field = [[GPBUnknownField alloc] initWithNumber:fieldNumber varint:value];
+  [fields_ addObject:field];
+  [field release];
+}
+
+- (void)addFieldNumber:(int32_t)fieldNumber fixed32:(uint32_t)value {
+  CHECK_FIELD_NUMBER(fieldNumber);
+  GPBUnknownField *field = [[GPBUnknownField alloc] initWithNumber:fieldNumber fixed32:value];
+  [fields_ addObject:field];
+  [field release];
+}
+
+- (void)addFieldNumber:(int32_t)fieldNumber fixed64:(uint64_t)value {
+  CHECK_FIELD_NUMBER(fieldNumber);
+  GPBUnknownField *field = [[GPBUnknownField alloc] initWithNumber:fieldNumber fixed64:value];
+  [fields_ addObject:field];
+  [field release];
+}
+
+- (void)addFieldNumber:(int32_t)fieldNumber lengthDelimited:(NSData *)value {
+  CHECK_FIELD_NUMBER(fieldNumber);
+  GPBUnknownField *field = [[GPBUnknownField alloc] initWithNumber:fieldNumber
+                                                   lengthDelimited:value];
+  [fields_ addObject:field];
+  [field release];
+}
+
+- (GPBUnknownFields *)addGroupWithFieldNumber:(int32_t)fieldNumber {
+  CHECK_FIELD_NUMBER(fieldNumber);
+  GPBUnknownFields *group = [[GPBUnknownFields alloc] init];
+  GPBUnknownField *field = [[GPBUnknownField alloc] initWithNumber:fieldNumber group:group];
+  [fields_ addObject:field];
+  [field release];
+  return [group autorelease];
+}
+
+#pragma mark - NSFastEnumeration protocol
+
+- (NSUInteger)countByEnumeratingWithState:(NSFastEnumerationState *)state
+                                  objects:(__unsafe_unretained id _Nonnull *)stackbuf
+                                    count:(NSUInteger)len {
+  return [fields_ countByEnumeratingWithState:state objects:stackbuf count:len];
+}
+
+@end
+
+@implementation GPBUnknownFields (AccessHelpers)
+
+- (BOOL)getFirst:(int32_t)fieldNumber varint:(nonnull uint64_t *)outValue {
+  CHECK_FIELD_NUMBER(fieldNumber);
+  for (GPBUnknownField *field in fields_) {
+    if (field.number == fieldNumber && field.type == GPBUnknownFieldTypeVarint) {
+      *outValue = field.varint;
+      return YES;
+    }
+  }
+  return NO;
+}
+
+- (BOOL)getFirst:(int32_t)fieldNumber fixed32:(nonnull uint32_t *)outValue {
+  CHECK_FIELD_NUMBER(fieldNumber);
+  for (GPBUnknownField *field in fields_) {
+    if (field.number == fieldNumber && field.type == GPBUnknownFieldTypeFixed32) {
+      *outValue = field.fixed32;
+      return YES;
+    }
+  }
+  return NO;
+}
+
+- (BOOL)getFirst:(int32_t)fieldNumber fixed64:(nonnull uint64_t *)outValue {
+  CHECK_FIELD_NUMBER(fieldNumber);
+  for (GPBUnknownField *field in fields_) {
+    if (field.number == fieldNumber && field.type == GPBUnknownFieldTypeFixed64) {
+      *outValue = field.fixed64;
+      return YES;
+    }
+  }
+  return NO;
+}
+
+- (nullable NSData *)firstLengthDelimited:(int32_t)fieldNumber {
+  CHECK_FIELD_NUMBER(fieldNumber);
+  for (GPBUnknownField *field in fields_) {
+    if (field.number == fieldNumber && field.type == GPBUnknownFieldTypeLengthDelimited) {
+      return field.lengthDelimited;
+    }
+  }
+  return nil;
+}
+
+- (nullable GPBUnknownFields *)firstGroup:(int32_t)fieldNumber {
+  CHECK_FIELD_NUMBER(fieldNumber);
+  for (GPBUnknownField *field in fields_) {
+    if (field.number == fieldNumber && field.type == GPBUnknownFieldTypeGroup) {
+      return field.group;
+    }
+  }
+  return nil;
+}
+
+#pragma clang diagnostic pop
+
+@end
diff --git a/objectivec/ProtocolBuffers_OSX.xcodeproj/project.pbxproj b/objectivec/ProtocolBuffers_OSX.xcodeproj/project.pbxproj
index c6466b2..b40bf9c 100644
--- a/objectivec/ProtocolBuffers_OSX.xcodeproj/project.pbxproj
+++ b/objectivec/ProtocolBuffers_OSX.xcodeproj/project.pbxproj
@@ -70,6 +70,10 @@
 		F4353D371AC06F10005A6198 /* GPBDictionaryTests+String.m in Sources */ = {isa = PBXBuildFile; fileRef = F4353D301AC06F10005A6198 /* GPBDictionaryTests+String.m */; };
 		F4353D381AC06F10005A6198 /* GPBDictionaryTests+UInt32.m in Sources */ = {isa = PBXBuildFile; fileRef = F4353D311AC06F10005A6198 /* GPBDictionaryTests+UInt32.m */; };
 		F4353D391AC06F10005A6198 /* GPBDictionaryTests+UInt64.m in Sources */ = {isa = PBXBuildFile; fileRef = F4353D321AC06F10005A6198 /* GPBDictionaryTests+UInt64.m */; };
+		F43ADD302C2F2B91005312E5 /* GPBUnknownFields.m in Sources */ = {isa = PBXBuildFile; fileRef = F43ADD2E2C2F2B91005312E5 /* GPBUnknownFields.m */; };
+		F43ADD312C2F2B91005312E5 /* GPBUnknownFields.h in Headers */ = {isa = PBXBuildFile; fileRef = F43ADD2F2C2F2B91005312E5 /* GPBUnknownFields.h */; };
+		F43ADD332C2F2BAD005312E5 /* GPBUnknownFieldsTest.m in Sources */ = {isa = PBXBuildFile; fileRef = F43ADD322C2F2BAD005312E5 /* GPBUnknownFieldsTest.m */; };
+		F43ADD432C2F381F005312E5 /* GPBCompileTest25.m in Sources */ = {isa = PBXBuildFile; fileRef = F43ADD422C2F381F005312E5 /* GPBCompileTest25.m */; };
 		F43C88D0191D77FC009E917D /* text_format_unittest_data.txt in Resources */ = {isa = PBXBuildFile; fileRef = F43C88CF191D77FC009E917D /* text_format_unittest_data.txt */; };
 		F4487C4D1A9F8E0200531423 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 1D30AB110D05D00D00671497 /* Foundation.framework */; };
 		F4487C521A9F8E4D00531423 /* GPBProtocolBuffers.m in Sources */ = {isa = PBXBuildFile; fileRef = 8BCF338814ED799900BC5317 /* GPBProtocolBuffers.m */; };
@@ -206,6 +210,10 @@
 		F4353D311AC06F10005A6198 /* GPBDictionaryTests+UInt32.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "GPBDictionaryTests+UInt32.m"; sourceTree = "<group>"; };
 		F4353D321AC06F10005A6198 /* GPBDictionaryTests+UInt64.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "GPBDictionaryTests+UInt64.m"; sourceTree = "<group>"; };
 		F43725911AC9832D004DCAFB /* GPBDictionary_PackagePrivate.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = GPBDictionary_PackagePrivate.h; sourceTree = "<group>"; };
+		F43ADD2E2C2F2B91005312E5 /* GPBUnknownFields.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = GPBUnknownFields.m; sourceTree = "<group>"; };
+		F43ADD2F2C2F2B91005312E5 /* GPBUnknownFields.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = GPBUnknownFields.h; sourceTree = "<group>"; };
+		F43ADD322C2F2BAD005312E5 /* GPBUnknownFieldsTest.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = GPBUnknownFieldsTest.m; sourceTree = "<group>"; };
+		F43ADD422C2F381F005312E5 /* GPBCompileTest25.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = GPBCompileTest25.m; sourceTree = "<group>"; };
 		F43C88CF191D77FC009E917D /* text_format_unittest_data.txt */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = text_format_unittest_data.txt; sourceTree = "<group>"; };
 		F4411BE71AF12FD700324B4A /* GPBArray_PackagePrivate.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = GPBArray_PackagePrivate.h; sourceTree = "<group>"; };
 		F4487C511A9F8E0200531423 /* libTestSingleSourceBuild.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libTestSingleSourceBuild.a; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -409,6 +417,8 @@
 				F4B6B8AF1A9CC98000892426 /* GPBUnknownField_PackagePrivate.h */,
 				7461B4AE0F94F99000A0C422 /* GPBUnknownField.h */,
 				7461B4AF0F94F99000A0C422 /* GPBUnknownField.m */,
+				F43ADD2F2C2F2B91005312E5 /* GPBUnknownFields.h */,
+				F43ADD2E2C2F2B91005312E5 /* GPBUnknownFields.m */,
 				F4B6B8B21A9CCBDA00892426 /* GPBUnknownFieldSet_PackagePrivate.h */,
 				7461B4E10F94F99000A0C422 /* GPBUnknownFieldSet.h */,
 				7461B4E20F94F99000A0C422 /* GPBUnknownFieldSet.m */,
@@ -478,6 +488,7 @@
 				F40EE48A206BF8B00071091A /* GPBCompileTest22.m */,
 				F40EE487206BF8B00071091A /* GPBCompileTest23.m */,
 				F4A92AFC2B88E105001E4F69 /* GPBCompileTest24.m */,
+				F43ADD422C2F381F005312E5 /* GPBCompileTest25.m */,
 				5102DABB1891A052002037B6 /* GPBConcurrencyTests.m */,
 				F4353D1C1AB8822D005A6198 /* GPBDescriptorTests.m */,
 				F4C4B9E21E1D974F00D3B61D /* GPBDictionaryTests.m */,
@@ -502,6 +513,7 @@
 				8BD3981E14BE59D70081D629 /* GPBUnittestProtos.m */,
 				F4F8D8811D789FCE002CE128 /* GPBUnittestProtos2.m */,
 				7461B6B80F94FDF900A0C422 /* GPBUnknownFieldSetTest.m */,
+				F43ADD322C2F2BAD005312E5 /* GPBUnknownFieldsTest.m */,
 				7461B6BA0F94FDF900A0C422 /* GPBUtilitiesTests.m */,
 				8B4248DB1A92933A00BC1EC6 /* GPBWellKnownTypesTest.m */,
 				7461B6BC0F94FDF900A0C422 /* GPBWireFormatTests.m */,
@@ -563,6 +575,7 @@
 			isa = PBXHeadersBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				F43ADD312C2F2B91005312E5 /* GPBUnknownFields.h in Headers */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -708,6 +721,7 @@
 				7461B53C0F94FB4E00A0C422 /* GPBCodedInputStream.m in Sources */,
 				F47CF93223D9006000C7B24C /* GPBWrappers.pbobjc.m in Sources */,
 				F47CF94123D902D500C7B24C /* GPBEmpty.pbobjc.m in Sources */,
+				F43ADD302C2F2B91005312E5 /* GPBUnknownFields.m in Sources */,
 				F47CF94623D902D500C7B24C /* GPBDuration.pbobjc.m in Sources */,
 				F47CF92F23D9006000C7B24C /* GPBSourceContext.pbobjc.m in Sources */,
 				7461B53D0F94FB4E00A0C422 /* GPBCodedOutputStream.m in Sources */,
@@ -769,9 +783,11 @@
 				5102DABC1891A073002037B6 /* GPBConcurrencyTests.m in Sources */,
 				F4487C751AADF7F500531423 /* GPBMessageTests+Runtime.m in Sources */,
 				F40EE4AC206BF8B90071091A /* GPBCompileTest02.m in Sources */,
+				F43ADD432C2F381F005312E5 /* GPBCompileTest25.m in Sources */,
 				F4353D351AC06F10005A6198 /* GPBDictionaryTests+Int32.m in Sources */,
 				F40EE4AF206BF8B90071091A /* GPBCompileTest05.m in Sources */,
 				F40EE4B8206BF8B90071091A /* GPBCompileTest14.m in Sources */,
+				F43ADD332C2F2BAD005312E5 /* GPBUnknownFieldsTest.m in Sources */,
 				8BBEA4B0147C727D00C4ADB7 /* GPBTestUtilities.m in Sources */,
 				F40EE4AE206BF8B90071091A /* GPBCompileTest04.m in Sources */,
 				F40EE4BA206BF8B90071091A /* GPBCompileTest16.m in Sources */,
diff --git a/objectivec/ProtocolBuffers_iOS.xcodeproj/project.pbxproj b/objectivec/ProtocolBuffers_iOS.xcodeproj/project.pbxproj
index 6e24f4c..2438b6a 100644
--- a/objectivec/ProtocolBuffers_iOS.xcodeproj/project.pbxproj
+++ b/objectivec/ProtocolBuffers_iOS.xcodeproj/project.pbxproj
@@ -70,6 +70,9 @@
 		F4353D451AC06F31005A6198 /* GPBDictionaryTests+String.m in Sources */ = {isa = PBXBuildFile; fileRef = F4353D3E1AC06F31005A6198 /* GPBDictionaryTests+String.m */; };
 		F4353D461AC06F31005A6198 /* GPBDictionaryTests+UInt32.m in Sources */ = {isa = PBXBuildFile; fileRef = F4353D3F1AC06F31005A6198 /* GPBDictionaryTests+UInt32.m */; };
 		F4353D471AC06F31005A6198 /* GPBDictionaryTests+UInt64.m in Sources */ = {isa = PBXBuildFile; fileRef = F4353D401AC06F31005A6198 /* GPBDictionaryTests+UInt64.m */; };
+		F43ADD352C2F2CE9005312E5 /* GPBUnknownFieldsTest.m in Sources */ = {isa = PBXBuildFile; fileRef = F43ADD342C2F2CE9005312E5 /* GPBUnknownFieldsTest.m */; };
+		F43ADD412C2F2D60005312E5 /* GPBUnknownFields.m in Sources */ = {isa = PBXBuildFile; fileRef = F43ADD362C2F2D06005312E5 /* GPBUnknownFields.m */; };
+		F43ADD472C2F387A005312E5 /* GPBCompileTest25.m in Sources */ = {isa = PBXBuildFile; fileRef = F43ADD462C2F387A005312E5 /* GPBCompileTest25.m */; };
 		F43C88D0191D77FC009E917D /* text_format_unittest_data.txt in Resources */ = {isa = PBXBuildFile; fileRef = F43C88CF191D77FC009E917D /* text_format_unittest_data.txt */; };
 		F4487C6A1A9F8F8100531423 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 1D30AB110D05D00D00671497 /* Foundation.framework */; };
 		F4487C6F1A9F8FFF00531423 /* GPBProtocolBuffers.m in Sources */ = {isa = PBXBuildFile; fileRef = 8BCF338814ED799900BC5317 /* GPBProtocolBuffers.m */; };
@@ -207,6 +210,10 @@
 		F4353D3F1AC06F31005A6198 /* GPBDictionaryTests+UInt32.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "GPBDictionaryTests+UInt32.m"; sourceTree = "<group>"; };
 		F4353D401AC06F31005A6198 /* GPBDictionaryTests+UInt64.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "GPBDictionaryTests+UInt64.m"; sourceTree = "<group>"; };
 		F43725921AC9835D004DCAFB /* GPBDictionary_PackagePrivate.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = GPBDictionary_PackagePrivate.h; sourceTree = "<group>"; };
+		F43ADD342C2F2CE9005312E5 /* GPBUnknownFieldsTest.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = GPBUnknownFieldsTest.m; sourceTree = "<group>"; };
+		F43ADD362C2F2D06005312E5 /* GPBUnknownFields.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = GPBUnknownFields.m; sourceTree = "<group>"; };
+		F43ADD372C2F2D06005312E5 /* GPBUnknownFields.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = GPBUnknownFields.h; sourceTree = "<group>"; };
+		F43ADD462C2F387A005312E5 /* GPBCompileTest25.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = GPBCompileTest25.m; sourceTree = "<group>"; };
 		F43C88CF191D77FC009E917D /* text_format_unittest_data.txt */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = text_format_unittest_data.txt; sourceTree = "<group>"; };
 		F4411BE81AF1301700324B4A /* GPBArray_PackagePrivate.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = GPBArray_PackagePrivate.h; sourceTree = "<group>"; };
 		F4487C6E1A9F8F8100531423 /* libTestSingleSourceBuild.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libTestSingleSourceBuild.a; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -415,6 +422,8 @@
 				F4B6B8B01A9CC99500892426 /* GPBUnknownField_PackagePrivate.h */,
 				7461B4AE0F94F99000A0C422 /* GPBUnknownField.h */,
 				7461B4AF0F94F99000A0C422 /* GPBUnknownField.m */,
+				F43ADD372C2F2D06005312E5 /* GPBUnknownFields.h */,
+				F43ADD362C2F2D06005312E5 /* GPBUnknownFields.m */,
 				F4B6B8B11A9CCBBB00892426 /* GPBUnknownFieldSet_PackagePrivate.h */,
 				7461B4E10F94F99000A0C422 /* GPBUnknownFieldSet.h */,
 				7461B4E20F94F99000A0C422 /* GPBUnknownFieldSet.m */,
@@ -484,6 +493,7 @@
 				F40EE4CF206BF9170071091A /* GPBCompileTest22.m */,
 				F40EE4CC206BF9170071091A /* GPBCompileTest23.m */,
 				F4A92AFE2B88E662001E4F69 /* GPBCompileTest24.m */,
+				F43ADD462C2F387A005312E5 /* GPBCompileTest25.m */,
 				5102DABB1891A052002037B6 /* GPBConcurrencyTests.m */,
 				F4353D1E1AB88243005A6198 /* GPBDescriptorTests.m */,
 				F4C4B9E51E1D97BB00D3B61D /* GPBDictionaryTests.m */,
@@ -508,6 +518,7 @@
 				8BD3981E14BE59D70081D629 /* GPBUnittestProtos.m */,
 				F4F8D8841D78A186002CE128 /* GPBUnittestProtos2.m */,
 				7461B6B80F94FDF900A0C422 /* GPBUnknownFieldSetTest.m */,
+				F43ADD342C2F2CE9005312E5 /* GPBUnknownFieldsTest.m */,
 				7461B6BA0F94FDF900A0C422 /* GPBUtilitiesTests.m */,
 				8B4248E51A929C9900BC1EC6 /* GPBWellKnownTypesTest.m */,
 				7461B6BC0F94FDF900A0C422 /* GPBWireFormatTests.m */,
@@ -715,6 +726,7 @@
 				F47CF96D23D903C600C7B24C /* GPBAny.pbobjc.m in Sources */,
 				F47CF96623D903C600C7B24C /* GPBSourceContext.pbobjc.m in Sources */,
 				F47CF96C23D903C600C7B24C /* GPBType.pbobjc.m in Sources */,
+				F43ADD412C2F2D60005312E5 /* GPBUnknownFields.m in Sources */,
 				F47CF96423D903C600C7B24C /* GPBStruct.pbobjc.m in Sources */,
 				F47CF96723D903C600C7B24C /* GPBEmpty.pbobjc.m in Sources */,
 				F4487C731A9F906200531423 /* GPBArray.m in Sources */,
@@ -776,9 +788,11 @@
 				5102DABC1891A073002037B6 /* GPBConcurrencyTests.m in Sources */,
 				F4487C771AADF84900531423 /* GPBMessageTests+Runtime.m in Sources */,
 				F40EE4F1206BF91E0071091A /* GPBCompileTest02.m in Sources */,
+				F43ADD472C2F387A005312E5 /* GPBCompileTest25.m in Sources */,
 				F4353D431AC06F31005A6198 /* GPBDictionaryTests+Int32.m in Sources */,
 				F40EE4F4206BF91E0071091A /* GPBCompileTest05.m in Sources */,
 				F40EE4FD206BF91E0071091A /* GPBCompileTest14.m in Sources */,
+				F43ADD352C2F2CE9005312E5 /* GPBUnknownFieldsTest.m in Sources */,
 				8BBEA4B0147C727D00C4ADB7 /* GPBTestUtilities.m in Sources */,
 				F40EE4F3206BF91E0071091A /* GPBCompileTest04.m in Sources */,
 				F40EE4FF206BF91E0071091A /* GPBCompileTest16.m in Sources */,
diff --git a/objectivec/ProtocolBuffers_tvOS.xcodeproj/project.pbxproj b/objectivec/ProtocolBuffers_tvOS.xcodeproj/project.pbxproj
index cc32112..d9d698d 100644
--- a/objectivec/ProtocolBuffers_tvOS.xcodeproj/project.pbxproj
+++ b/objectivec/ProtocolBuffers_tvOS.xcodeproj/project.pbxproj
@@ -70,6 +70,10 @@
 		F4353D451AC06F31005A6198 /* GPBDictionaryTests+String.m in Sources */ = {isa = PBXBuildFile; fileRef = F4353D3E1AC06F31005A6198 /* GPBDictionaryTests+String.m */; };
 		F4353D461AC06F31005A6198 /* GPBDictionaryTests+UInt32.m in Sources */ = {isa = PBXBuildFile; fileRef = F4353D3F1AC06F31005A6198 /* GPBDictionaryTests+UInt32.m */; };
 		F4353D471AC06F31005A6198 /* GPBDictionaryTests+UInt64.m in Sources */ = {isa = PBXBuildFile; fileRef = F4353D401AC06F31005A6198 /* GPBDictionaryTests+UInt64.m */; };
+		F43ADD3A2C2F2D26005312E5 /* GPBUnknownFieldsTest.m in Sources */ = {isa = PBXBuildFile; fileRef = F43ADD392C2F2D26005312E5 /* GPBUnknownFieldsTest.m */; };
+		F43ADD3D2C2F2D3D005312E5 /* GPBUnknownFields.m in Sources */ = {isa = PBXBuildFile; fileRef = F43ADD3B2C2F2D3D005312E5 /* GPBUnknownFields.m */; };
+		F43ADD3E2C2F2D3D005312E5 /* GPBUnknownFields.h in Headers */ = {isa = PBXBuildFile; fileRef = F43ADD3C2C2F2D3D005312E5 /* GPBUnknownFields.h */; };
+		F43ADD492C2F389D005312E5 /* GPBCompileTest25.m in Sources */ = {isa = PBXBuildFile; fileRef = F43ADD482C2F389D005312E5 /* GPBCompileTest25.m */; };
 		F43C88D0191D77FC009E917D /* text_format_unittest_data.txt in Resources */ = {isa = PBXBuildFile; fileRef = F43C88CF191D77FC009E917D /* text_format_unittest_data.txt */; };
 		F4487C6A1A9F8F8100531423 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 1D30AB110D05D00D00671497 /* Foundation.framework */; };
 		F4487C6F1A9F8FFF00531423 /* GPBProtocolBuffers.m in Sources */ = {isa = PBXBuildFile; fileRef = 8BCF338814ED799900BC5317 /* GPBProtocolBuffers.m */; };
@@ -207,6 +211,10 @@
 		F4353D3F1AC06F31005A6198 /* GPBDictionaryTests+UInt32.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "GPBDictionaryTests+UInt32.m"; sourceTree = "<group>"; };
 		F4353D401AC06F31005A6198 /* GPBDictionaryTests+UInt64.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "GPBDictionaryTests+UInt64.m"; sourceTree = "<group>"; };
 		F43725921AC9835D004DCAFB /* GPBDictionary_PackagePrivate.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = GPBDictionary_PackagePrivate.h; sourceTree = "<group>"; };
+		F43ADD392C2F2D26005312E5 /* GPBUnknownFieldsTest.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = GPBUnknownFieldsTest.m; sourceTree = "<group>"; };
+		F43ADD3B2C2F2D3D005312E5 /* GPBUnknownFields.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = GPBUnknownFields.m; sourceTree = "<group>"; };
+		F43ADD3C2C2F2D3D005312E5 /* GPBUnknownFields.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = GPBUnknownFields.h; sourceTree = "<group>"; };
+		F43ADD482C2F389D005312E5 /* GPBCompileTest25.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = GPBCompileTest25.m; sourceTree = "<group>"; };
 		F43C88CF191D77FC009E917D /* text_format_unittest_data.txt */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = text_format_unittest_data.txt; sourceTree = "<group>"; };
 		F4411BE81AF1301700324B4A /* GPBArray_PackagePrivate.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = GPBArray_PackagePrivate.h; sourceTree = "<group>"; };
 		F4487C6E1A9F8F8100531423 /* libTestSingleSourceBuild.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libTestSingleSourceBuild.a; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -415,6 +423,8 @@
 				F4B6B8B01A9CC99500892426 /* GPBUnknownField_PackagePrivate.h */,
 				7461B4AE0F94F99000A0C422 /* GPBUnknownField.h */,
 				7461B4AF0F94F99000A0C422 /* GPBUnknownField.m */,
+				F43ADD3C2C2F2D3D005312E5 /* GPBUnknownFields.h */,
+				F43ADD3B2C2F2D3D005312E5 /* GPBUnknownFields.m */,
 				F4B6B8B11A9CCBBB00892426 /* GPBUnknownFieldSet_PackagePrivate.h */,
 				7461B4E10F94F99000A0C422 /* GPBUnknownFieldSet.h */,
 				7461B4E20F94F99000A0C422 /* GPBUnknownFieldSet.m */,
@@ -484,6 +494,7 @@
 				F40EE4CF206BF9170071091A /* GPBCompileTest22.m */,
 				F40EE4CC206BF9170071091A /* GPBCompileTest23.m */,
 				F4A92B002B88E683001E4F69 /* GPBCompileTest24.m */,
+				F43ADD482C2F389D005312E5 /* GPBCompileTest25.m */,
 				5102DABB1891A052002037B6 /* GPBConcurrencyTests.m */,
 				F4353D1E1AB88243005A6198 /* GPBDescriptorTests.m */,
 				F4C4B9E51E1D97BB00D3B61D /* GPBDictionaryTests.m */,
@@ -508,6 +519,7 @@
 				8BD3981E14BE59D70081D629 /* GPBUnittestProtos.m */,
 				F4F8D8841D78A186002CE128 /* GPBUnittestProtos2.m */,
 				7461B6B80F94FDF900A0C422 /* GPBUnknownFieldSetTest.m */,
+				F43ADD392C2F2D26005312E5 /* GPBUnknownFieldsTest.m */,
 				7461B6BA0F94FDF900A0C422 /* GPBUtilitiesTests.m */,
 				8B4248E51A929C9900BC1EC6 /* GPBWellKnownTypesTest.m */,
 				7461B6BC0F94FDF900A0C422 /* GPBWireFormatTests.m */,
@@ -569,6 +581,7 @@
 			isa = PBXHeadersBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				F43ADD3E2C2F2D3D005312E5 /* GPBUnknownFields.h in Headers */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -715,6 +728,7 @@
 				F4487C731A9F906200531423 /* GPBArray.m in Sources */,
 				F47CF98923D904E600C7B24C /* GPBStruct.pbobjc.m in Sources */,
 				F47CF98623D904E600C7B24C /* GPBEmpty.pbobjc.m in Sources */,
+				F43ADD3D2C2F2D3D005312E5 /* GPBUnknownFields.m in Sources */,
 				7461B53D0F94FB4E00A0C422 /* GPBCodedOutputStream.m in Sources */,
 				F47CF98523D904E600C7B24C /* GPBApi.pbobjc.m in Sources */,
 				7461B5490F94FB4E00A0C422 /* GPBExtensionRegistry.m in Sources */,
@@ -776,9 +790,11 @@
 				5102DABC1891A073002037B6 /* GPBConcurrencyTests.m in Sources */,
 				F4487C771AADF84900531423 /* GPBMessageTests+Runtime.m in Sources */,
 				F40EE4F1206BF91E0071091A /* GPBCompileTest02.m in Sources */,
+				F43ADD492C2F389D005312E5 /* GPBCompileTest25.m in Sources */,
 				F4353D431AC06F31005A6198 /* GPBDictionaryTests+Int32.m in Sources */,
 				F40EE4F4206BF91E0071091A /* GPBCompileTest05.m in Sources */,
 				F40EE4FD206BF91E0071091A /* GPBCompileTest14.m in Sources */,
+				F43ADD3A2C2F2D26005312E5 /* GPBUnknownFieldsTest.m in Sources */,
 				8BBEA4B0147C727D00C4ADB7 /* GPBTestUtilities.m in Sources */,
 				F40EE4F3206BF91E0071091A /* GPBCompileTest04.m in Sources */,
 				F40EE4FF206BF91E0071091A /* GPBCompileTest16.m in Sources */,
diff --git a/objectivec/Tests/GPBCompileTest25.m b/objectivec/Tests/GPBCompileTest25.m
new file mode 100644
index 0000000..450795b
--- /dev/null
+++ b/objectivec/Tests/GPBCompileTest25.m
@@ -0,0 +1,15 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2024 Google Inc.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+// This is a test including a single public header to ensure things build.
+// It helps test that imports are complete/ordered correctly.
+
+#import "GPBUnknownFields.h"
+
+// Something in the body of this file so the compiler/linker won't complain
+// about an empty .o file.
+__attribute__((visibility("default"))) char dummy_symbol_25 = 0;
diff --git a/objectivec/Tests/GPBUnknownFieldsTest.m b/objectivec/Tests/GPBUnknownFieldsTest.m
new file mode 100644
index 0000000..552c21d
--- /dev/null
+++ b/objectivec/Tests/GPBUnknownFieldsTest.m
@@ -0,0 +1,514 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2024 Google Inc.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+#import "GPBTestUtilities.h"
+#import "GPBUnknownField.h"
+#import "GPBUnknownFields.h"
+#import "objectivec/Tests/Unittest.pbobjc.h"
+
+@interface UnknownFieldsTest : GPBTestCase
+@end
+
+@implementation UnknownFieldsTest
+
+- (void)testEmptyAndClear {
+  GPBUnknownFields* ufs = [[[GPBUnknownFields alloc] init] autorelease];
+  XCTAssertTrue(ufs.empty);
+
+  [ufs addFieldNumber:1 varint:1];
+  XCTAssertFalse(ufs.empty);
+  [ufs clear];
+  XCTAssertTrue(ufs.empty);
+
+  [ufs addFieldNumber:1 fixed32:1];
+  XCTAssertFalse(ufs.empty);
+  [ufs clear];
+  XCTAssertTrue(ufs.empty);
+
+  [ufs addFieldNumber:1 fixed64:1];
+  XCTAssertFalse(ufs.empty);
+  [ufs clear];
+  XCTAssertTrue(ufs.empty);
+
+  [ufs addFieldNumber:1 lengthDelimited:[NSData data]];
+  XCTAssertFalse(ufs.empty);
+  [ufs clear];
+  XCTAssertTrue(ufs.empty);
+
+  GPBUnknownFields* group = [ufs addGroupWithFieldNumber:1];
+  XCTAssertNotNil(group);
+  XCTAssertFalse(ufs.empty);
+}
+
+- (void)testEqualityAndHash {
+  // Empty
+
+  GPBUnknownFields* ufs1 = [[[GPBUnknownFields alloc] init] autorelease];
+  XCTAssertTrue([ufs1 isEqual:ufs1]);
+  XCTAssertFalse([ufs1 isEqual:@"foo"]);
+  GPBUnknownFields* ufs2 = [[[GPBUnknownFields alloc] init] autorelease];
+  XCTAssertEqualObjects(ufs1, ufs2);
+  XCTAssertEqual([ufs1 hash], [ufs2 hash]);
+
+  // Varint
+
+  [ufs1 addFieldNumber:1 varint:1];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+  [ufs2 addFieldNumber:1 varint:1];
+  XCTAssertEqualObjects(ufs1, ufs2);
+  XCTAssertEqual([ufs1 hash], [ufs2 hash]);
+
+  // Fixed32
+
+  [ufs1 addFieldNumber:2 fixed32:1];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+  [ufs2 addFieldNumber:2 fixed32:1];
+  XCTAssertEqualObjects(ufs1, ufs2);
+  XCTAssertEqual([ufs1 hash], [ufs2 hash]);
+
+  // Fixed64
+
+  [ufs1 addFieldNumber:3 fixed64:1];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+  [ufs2 addFieldNumber:3 fixed64:1];
+  XCTAssertEqualObjects(ufs1, ufs2);
+  XCTAssertEqual([ufs1 hash], [ufs2 hash]);
+
+  // LengthDelimited
+
+  [ufs1 addFieldNumber:4 lengthDelimited:DataFromCStr("foo")];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+  [ufs2 addFieldNumber:4 lengthDelimited:DataFromCStr("foo")];
+  XCTAssertEqualObjects(ufs1, ufs2);
+  XCTAssertEqual([ufs1 hash], [ufs2 hash]);
+
+  // Group
+
+  GPBUnknownFields* group1 = [ufs1 addGroupWithFieldNumber:5];
+  [group1 addFieldNumber:10 varint:10];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+  GPBUnknownFields* group2 = [ufs2 addGroupWithFieldNumber:5];
+  [group2 addFieldNumber:10 varint:10];
+  XCTAssertEqualObjects(ufs1, ufs2);
+  XCTAssertEqual([ufs1 hash], [ufs2 hash]);
+}
+
+- (void)testInequality_Values {
+  // Same field number and type, different values.
+
+  GPBUnknownFields* ufs1 = [[[GPBUnknownFields alloc] init] autorelease];
+  GPBUnknownFields* ufs2 = [[[GPBUnknownFields alloc] init] autorelease];
+
+  [ufs1 addFieldNumber:1 varint:1];
+  [ufs2 addFieldNumber:1 varint:2];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+
+  [ufs1 clear];
+  [ufs2 clear];
+  XCTAssertEqualObjects(ufs1, ufs2);
+
+  [ufs1 addFieldNumber:1 fixed32:1];
+  [ufs2 addFieldNumber:1 fixed32:2];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+
+  [ufs1 clear];
+  [ufs2 clear];
+  XCTAssertEqualObjects(ufs1, ufs2);
+
+  [ufs1 addFieldNumber:1 fixed64:1];
+  [ufs2 addFieldNumber:1 fixed64:2];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+
+  [ufs1 clear];
+  [ufs2 clear];
+  XCTAssertEqualObjects(ufs1, ufs2);
+
+  [ufs1 addFieldNumber:1 lengthDelimited:DataFromCStr("foo")];
+  [ufs2 addFieldNumber:1 lengthDelimited:DataFromCStr("bar")];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+
+  [ufs1 clear];
+  [ufs2 clear];
+  XCTAssertEqualObjects(ufs1, ufs2);
+
+  GPBUnknownFields* group1 = [ufs1 addGroupWithFieldNumber:1];
+  GPBUnknownFields* group2 = [ufs2 addGroupWithFieldNumber:1];
+  [group1 addFieldNumber:10 varint:10];
+  [group2 addFieldNumber:10 varint:20];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+  XCTAssertNotEqualObjects(group1, group2);
+}
+
+- (void)testInequality_FieldNumbers {
+  // Same type and value, different field numbers.
+
+  GPBUnknownFields* ufs1 = [[[GPBUnknownFields alloc] init] autorelease];
+  GPBUnknownFields* ufs2 = [[[GPBUnknownFields alloc] init] autorelease];
+
+  [ufs1 addFieldNumber:1 varint:1];
+  [ufs2 addFieldNumber:2 varint:1];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+
+  [ufs1 clear];
+  [ufs2 clear];
+  XCTAssertEqualObjects(ufs1, ufs2);
+
+  [ufs1 addFieldNumber:1 fixed32:1];
+  [ufs2 addFieldNumber:2 fixed32:1];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+
+  [ufs1 clear];
+  [ufs2 clear];
+  XCTAssertEqualObjects(ufs1, ufs2);
+
+  [ufs1 addFieldNumber:1 fixed64:1];
+  [ufs2 addFieldNumber:2 fixed64:1];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+
+  [ufs1 clear];
+  [ufs2 clear];
+  XCTAssertEqualObjects(ufs1, ufs2);
+
+  [ufs1 addFieldNumber:1 lengthDelimited:DataFromCStr("foo")];
+  [ufs2 addFieldNumber:2 lengthDelimited:DataFromCStr("fod")];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+
+  [ufs1 clear];
+  [ufs2 clear];
+  XCTAssertEqualObjects(ufs1, ufs2);
+
+  GPBUnknownFields* group1 = [ufs1 addGroupWithFieldNumber:1];
+  GPBUnknownFields* group2 = [ufs2 addGroupWithFieldNumber:2];
+  [group1 addFieldNumber:10 varint:10];
+  [group2 addFieldNumber:10 varint:10];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+  XCTAssertEqualObjects(group1, group2);
+}
+
+- (void)testInequality_Types {
+  // Same field number and value when possible, different types.
+
+  GPBUnknownFields* ufs1 = [[[GPBUnknownFields alloc] init] autorelease];
+  GPBUnknownFields* ufs2 = [[[GPBUnknownFields alloc] init] autorelease];
+
+  [ufs1 addFieldNumber:1 varint:1];
+  [ufs2 addFieldNumber:1 fixed32:1];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+
+  [ufs1 clear];
+  [ufs2 clear];
+  XCTAssertEqualObjects(ufs1, ufs2);
+
+  [ufs1 addFieldNumber:1 fixed32:1];
+  [ufs2 addFieldNumber:1 fixed64:1];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+
+  [ufs1 clear];
+  [ufs2 clear];
+  XCTAssertEqualObjects(ufs1, ufs2);
+
+  [ufs1 addFieldNumber:1 fixed64:1];
+  [ufs2 addFieldNumber:1 varint:1];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+
+  [ufs1 clear];
+  [ufs2 clear];
+  XCTAssertEqualObjects(ufs1, ufs2);
+
+  [ufs1 addFieldNumber:1 lengthDelimited:DataFromCStr("foo")];
+  [ufs2 addFieldNumber:1 varint:1];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+
+  [ufs1 clear];
+  [ufs2 clear];
+  XCTAssertEqualObjects(ufs1, ufs2);
+
+  GPBUnknownFields* group1 = [ufs1 addGroupWithFieldNumber:1];
+  [group1 addFieldNumber:10 varint:10];
+  [ufs2 addFieldNumber:1 varint:1];
+  XCTAssertNotEqualObjects(ufs1, ufs2);
+}
+
+- (void)testGetFirst {
+  GPBUnknownFields* ufs = [[[GPBUnknownFields alloc] init] autorelease];
+  XCTAssertEqual(0U, ufs.count);
+  [ufs addFieldNumber:1 varint:1];
+  XCTAssertEqual(1U, ufs.count);
+  [ufs addFieldNumber:1 varint:2];
+  XCTAssertEqual(2U, ufs.count);
+  [ufs addFieldNumber:1 fixed32:3];
+  XCTAssertEqual(3U, ufs.count);
+  [ufs addFieldNumber:1 fixed32:4];
+  XCTAssertEqual(4U, ufs.count);
+  [ufs addFieldNumber:1 fixed64:5];
+  XCTAssertEqual(5U, ufs.count);
+  [ufs addFieldNumber:1 fixed64:6];
+  XCTAssertEqual(6U, ufs.count);
+  [ufs addFieldNumber:1 lengthDelimited:DataFromCStr("foo")];
+  XCTAssertEqual(7U, ufs.count);
+  [ufs addFieldNumber:1 lengthDelimited:DataFromCStr("bar")];
+  XCTAssertEqual(8U, ufs.count);
+  GPBUnknownFields* group1 = [ufs addGroupWithFieldNumber:1];
+  XCTAssertNotNil(group1);
+  XCTAssertEqual(9U, ufs.count);
+  GPBUnknownFields* group2 = [ufs addGroupWithFieldNumber:1];
+  XCTAssertNotNil(group2);
+  XCTAssertTrue(group1 != group2);  // Different objects
+  XCTAssertEqual(10U, ufs.count);
+
+  [ufs addFieldNumber:11 varint:11];
+  [ufs addFieldNumber:12 fixed32:12];
+  [ufs addFieldNumber:13 fixed64:13];
+  [ufs addFieldNumber:14 lengthDelimited:DataFromCStr("foo2")];
+  GPBUnknownFields* group3 = [ufs addGroupWithFieldNumber:15];
+  XCTAssertNotNil(group3);
+  XCTAssertTrue(group3 != group1);  // Different objects
+  XCTAssertTrue(group3 != group2);  // Different objects
+  XCTAssertEqual(15U, ufs.count);
+
+  uint64_t varint = 0;
+  XCTAssertTrue([ufs getFirst:1 varint:&varint]);
+  XCTAssertEqual(1U, varint);
+  XCTAssertTrue([ufs getFirst:11 varint:&varint]);
+  XCTAssertEqual(11U, varint);
+  XCTAssertFalse([ufs getFirst:12 varint:&varint]);  // Different type
+  XCTAssertFalse([ufs getFirst:99 varint:&varint]);  // Not present
+
+  uint32_t fixed32 = 0;
+  XCTAssertTrue([ufs getFirst:1 fixed32:&fixed32]);
+  XCTAssertEqual(3U, fixed32);
+  XCTAssertTrue([ufs getFirst:12 fixed32:&fixed32]);
+  XCTAssertEqual(12U, fixed32);
+  XCTAssertFalse([ufs getFirst:11 fixed32:&fixed32]);  // Different type
+  XCTAssertFalse([ufs getFirst:99 fixed32:&fixed32]);  // Not present
+
+  uint64_t fixed64 = 0;
+  XCTAssertTrue([ufs getFirst:1 fixed64:&fixed64]);
+  XCTAssertEqual(5U, fixed64);
+  XCTAssertTrue([ufs getFirst:13 fixed64:&fixed64]);
+  XCTAssertEqual(13U, fixed64);
+  XCTAssertFalse([ufs getFirst:11 fixed64:&fixed64]);  // Different type
+  XCTAssertFalse([ufs getFirst:99 fixed64:&fixed64]);  // Not present
+
+  XCTAssertEqualObjects(DataFromCStr("foo"), [ufs firstLengthDelimited:1]);
+  XCTAssertEqualObjects(DataFromCStr("foo2"), [ufs firstLengthDelimited:14]);
+  XCTAssertNil([ufs firstLengthDelimited:11]);  // Different type
+  XCTAssertNil([ufs firstLengthDelimited:99]);  // Not present
+
+  XCTAssertTrue(group1 == [ufs firstGroup:1]);   // Testing ptr, exact object
+  XCTAssertTrue(group3 == [ufs firstGroup:15]);  // Testing ptr, exact object
+  XCTAssertNil([ufs firstGroup:11]);             // Different type
+  XCTAssertNil([ufs firstGroup:99]);             // Not present
+}
+
+- (void)testGetFields {
+  GPBUnknownFields* ufs = [[[GPBUnknownFields alloc] init] autorelease];
+  [ufs addFieldNumber:1 varint:1];
+  [ufs addFieldNumber:2 varint:2];
+  [ufs addFieldNumber:1 fixed32:3];
+  [ufs addFieldNumber:2 fixed32:4];
+  [ufs addFieldNumber:1 fixed64:5];
+  [ufs addFieldNumber:3 fixed64:6];
+  [ufs addFieldNumber:1 lengthDelimited:DataFromCStr("foo")];
+  [ufs addFieldNumber:2 lengthDelimited:DataFromCStr("bar")];
+  GPBUnknownFields* group1 = [ufs addGroupWithFieldNumber:1];
+  GPBUnknownFields* group2 = [ufs addGroupWithFieldNumber:3];
+
+  NSArray<GPBUnknownField*>* fields1 = [ufs fields:1];
+  XCTAssertEqual(fields1.count, 5);
+  GPBUnknownField* field = fields1[0];
+  XCTAssertEqual(field.number, 1);
+  XCTAssertEqual(field.type, GPBUnknownFieldTypeVarint);
+  XCTAssertEqual(field.varint, 1);
+  field = fields1[1];
+  XCTAssertEqual(field.number, 1);
+  XCTAssertEqual(field.type, GPBUnknownFieldTypeFixed32);
+  XCTAssertEqual(field.fixed32, 3);
+  field = fields1[2];
+  XCTAssertEqual(field.number, 1);
+  XCTAssertEqual(field.type, GPBUnknownFieldTypeFixed64);
+  XCTAssertEqual(field.fixed64, 5);
+  field = fields1[3];
+  XCTAssertEqual(field.number, 1);
+  XCTAssertEqual(field.type, GPBUnknownFieldTypeLengthDelimited);
+  XCTAssertEqualObjects(field.lengthDelimited, DataFromCStr("foo"));
+  field = fields1[4];
+  XCTAssertEqual(field.number, 1);
+  XCTAssertEqual(field.type, GPBUnknownFieldTypeGroup);
+  XCTAssertTrue(field.group == group1);  // Exact object.
+
+  NSArray<GPBUnknownField*>* fields2 = [ufs fields:2];
+  XCTAssertEqual(fields2.count, 3);
+  field = fields2[0];
+  XCTAssertEqual(field.number, 2);
+  XCTAssertEqual(field.type, GPBUnknownFieldTypeVarint);
+  XCTAssertEqual(field.varint, 2);
+  field = fields2[1];
+  XCTAssertEqual(field.number, 2);
+  XCTAssertEqual(field.type, GPBUnknownFieldTypeFixed32);
+  XCTAssertEqual(field.fixed32, 4);
+  field = fields2[2];
+  XCTAssertEqual(field.number, 2);
+  XCTAssertEqual(field.type, GPBUnknownFieldTypeLengthDelimited);
+  XCTAssertEqualObjects(field.lengthDelimited, DataFromCStr("bar"));
+
+  NSArray<GPBUnknownField*>* fields3 = [ufs fields:3];
+  XCTAssertEqual(fields3.count, 2);
+  field = fields3[0];
+  XCTAssertEqual(field.number, 3);
+  XCTAssertEqual(field.type, GPBUnknownFieldTypeFixed64);
+  XCTAssertEqual(field.fixed64, 6);
+  field = fields3[1];
+  XCTAssertEqual(field.number, 3);
+  XCTAssertEqual(field.type, GPBUnknownFieldTypeGroup);
+  XCTAssertTrue(field.group == group2);  // Exact object.
+
+  XCTAssertNil([ufs fields:99]);  // Not present
+}
+
+- (void)testFastEnumeration {
+  GPBUnknownFields* ufs = [[[GPBUnknownFields alloc] init] autorelease];
+  [ufs addFieldNumber:1 varint:1];
+  [ufs addFieldNumber:2 varint:2];
+  [ufs addFieldNumber:1 fixed32:3];
+  [ufs addFieldNumber:2 fixed32:4];
+  [ufs addFieldNumber:1 fixed64:5];
+  [ufs addFieldNumber:3 fixed64:6];
+  [ufs addFieldNumber:1 lengthDelimited:DataFromCStr("foo")];
+  [ufs addFieldNumber:2 lengthDelimited:DataFromCStr("bar")];
+  GPBUnknownFields* group1 = [ufs addGroupWithFieldNumber:1];
+  GPBUnknownFields* group2 = [ufs addGroupWithFieldNumber:3];
+
+  // The order added nothing to do with field numbers.
+  NSInteger loop = 0;
+  for (GPBUnknownField* field in ufs) {
+    ++loop;
+    switch (loop) {
+      case 1:
+        XCTAssertEqual(field.number, 1);
+        XCTAssertEqual(field.type, GPBUnknownFieldTypeVarint);
+        XCTAssertEqual(field.varint, 1);
+        break;
+      case 2:
+        XCTAssertEqual(field.number, 2);
+        XCTAssertEqual(field.type, GPBUnknownFieldTypeVarint);
+        XCTAssertEqual(field.varint, 2);
+        break;
+      case 3:
+        XCTAssertEqual(field.number, 1);
+        XCTAssertEqual(field.type, GPBUnknownFieldTypeFixed32);
+        XCTAssertEqual(field.fixed32, 3);
+        break;
+      case 4:
+        XCTAssertEqual(field.number, 2);
+        XCTAssertEqual(field.type, GPBUnknownFieldTypeFixed32);
+        XCTAssertEqual(field.fixed32, 4);
+        break;
+      case 5:
+        XCTAssertEqual(field.number, 1);
+        XCTAssertEqual(field.type, GPBUnknownFieldTypeFixed64);
+        XCTAssertEqual(field.fixed64, 5);
+        break;
+      case 6:
+        XCTAssertEqual(field.number, 3);
+        XCTAssertEqual(field.type, GPBUnknownFieldTypeFixed64);
+        XCTAssertEqual(field.fixed64, 6);
+        break;
+      case 7:
+        XCTAssertEqual(field.number, 1);
+        XCTAssertEqual(field.type, GPBUnknownFieldTypeLengthDelimited);
+        XCTAssertEqualObjects(field.lengthDelimited, DataFromCStr("foo"));
+        break;
+      case 8:
+        XCTAssertEqual(field.number, 2);
+        XCTAssertEqual(field.type, GPBUnknownFieldTypeLengthDelimited);
+        XCTAssertEqualObjects(field.lengthDelimited, DataFromCStr("bar"));
+        break;
+      case 9:
+        XCTAssertEqual(field.number, 1);
+        XCTAssertEqual(field.type, GPBUnknownFieldTypeGroup);
+        XCTAssertTrue(field.group == group1);  // Exact object.
+        break;
+      case 10:
+        XCTAssertEqual(field.number, 3);
+        XCTAssertEqual(field.type, GPBUnknownFieldTypeGroup);
+        XCTAssertTrue(field.group == group2);  // Exact object.
+        break;
+      default:
+        XCTFail(@"Unexpected");
+        break;
+    }
+  }
+  XCTAssertEqual(loop, 10);
+}
+
+- (void)testDescriptions {
+  // Exercise description for completeness.
+  GPBUnknownFields* ufs = [[[GPBUnknownFields alloc] init] autorelease];
+  [ufs addFieldNumber:1 varint:1];
+  [ufs addFieldNumber:2 fixed32:1];
+  [ufs addFieldNumber:1 fixed64:1];
+  [ufs addFieldNumber:4 lengthDelimited:DataFromCStr("foo")];
+  [[ufs addGroupWithFieldNumber:5] addFieldNumber:10 varint:10];
+  XCTAssertTrue(ufs.description.length > 10);
+  for (GPBUnknownField* field in ufs) {
+    XCTAssertTrue(field.description.length > 10);
+  }
+}
+
+- (void)testInvalidFieldNumbers {
+  GPBUnknownFields* ufs = [[[GPBUnknownFields alloc] init] autorelease];
+
+  XCTAssertThrowsSpecificNamed([ufs addFieldNumber:0 varint:1], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs addFieldNumber:0 fixed32:1], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs addFieldNumber:0 fixed64:1], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs addFieldNumber:0 lengthDelimited:[NSData data]], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs addGroupWithFieldNumber:0], NSException,
+                               NSInvalidArgumentException);
+
+  XCTAssertThrowsSpecificNamed([ufs addFieldNumber:-1 varint:1], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs addFieldNumber:-1 fixed32:1], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs addFieldNumber:-1 fixed64:1], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs addFieldNumber:-1 lengthDelimited:[NSData data]], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs addGroupWithFieldNumber:-1], NSException,
+                               NSInvalidArgumentException);
+
+  uint64_t varint;
+  uint32_t fixed32;
+  uint64_t fixed64;
+  XCTAssertThrowsSpecificNamed([ufs getFirst:0 varint:&varint], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs getFirst:0 fixed32:&fixed32], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs getFirst:0 fixed64:&fixed64], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs firstLengthDelimited:0], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs firstGroup:0], NSException, NSInvalidArgumentException);
+
+  XCTAssertThrowsSpecificNamed([ufs getFirst:-1 varint:&varint], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs getFirst:-1 fixed32:&fixed32], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs getFirst:-1 fixed64:&fixed64], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs firstLengthDelimited:-1], NSException,
+                               NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs firstGroup:-1], NSException, NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs fields:0], NSException, NSInvalidArgumentException);
+  XCTAssertThrowsSpecificNamed([ufs fields:-1], NSException, NSInvalidArgumentException);
+}
+
+@end