Added Changelog entries for Google-internal changes.
diff --git a/CHANGES.txt b/CHANGES.txt
index 6234f16..a0335e0 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,3 +1,13 @@
+Unreleased Changes
+
+ C++:
+ * Enabled heterogeneous lookup for std::string keys in maps.
+ * Improved the randomness of map ordering.
+
+ Python:
+ * Improved the error message when AttributeError is returned from __getattr__
+ in EnumTypeWrapper.
+
2020-05-12 version 3.12.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
Protocol Compiler