diff --git a/include/polarssl/aes.h b/include/polarssl/aes.h
index 61ad457..8268390 100644
--- a/include/polarssl/aes.h
+++ b/include/polarssl/aes.h
@@ -74,7 +74,7 @@
  * \param input    16-byte input block
  * \param output   16-byte output block
  *
- * \return         0
+ * \return         0 if successful
  */
 int aes_crypt_ecb( aes_context *ctx,
                     int mode,
@@ -113,7 +113,7 @@
  * \param input    buffer holding the input data
  * \param output   buffer holding the output data
  *
- * \return         0
+ * \return         0 if successful
  */
 int aes_crypt_cfb128( aes_context *ctx,
                        int mode,
diff --git a/include/polarssl/arc4.h b/include/polarssl/arc4.h
index f6b9f13..14abe39 100644
--- a/include/polarssl/arc4.h
+++ b/include/polarssl/arc4.h
@@ -55,7 +55,7 @@
  * \param input    buffer holding the input data
  * \param output   buffer for the output data
  *
- * \return         0
+ * \return         0 if successful
  */
 int arc4_crypt( arc4_context *ctx, int length, const unsigned char *input,
                 unsigned char *output );
diff --git a/include/polarssl/camellia.h b/include/polarssl/camellia.h
index e9ded15..ed05990 100644
--- a/include/polarssl/camellia.h
+++ b/include/polarssl/camellia.h
@@ -78,7 +78,7 @@
  * \param input    16-byte input block
  * \param output   16-byte output block
  * 
- * \return         0
+ * \return         0 if successful
  */
 int camellia_crypt_ecb( camellia_context *ctx,
                     int mode,
diff --git a/include/polarssl/des.h b/include/polarssl/des.h
index a655a15..04fdf67 100644
--- a/include/polarssl/des.h
+++ b/include/polarssl/des.h
@@ -107,7 +107,7 @@
  * \param input    64-bit input block
  * \param output   64-bit output block
  *
- * \return         0
+ * \return         0 if successful
  */
 int des_crypt_ecb( des_context *ctx,
                     const unsigned char input[8],
@@ -137,7 +137,7 @@
  * \param input    64-bit input block
  * \param output   64-bit output block
  *
- * \return         0
+ * \return         0 if successful
  */
 int des3_crypt_ecb( des3_context *ctx,
                      const unsigned char input[8],
diff --git a/include/polarssl/xtea.h b/include/polarssl/xtea.h
index 12a9455..21f0edf 100644
--- a/include/polarssl/xtea.h
+++ b/include/polarssl/xtea.h
@@ -61,7 +61,7 @@
  * \param input    8-byte input block
  * \param output   8-byte output block
  *
- * \return         0
+ * \return         0 if successful
  */
 int xtea_crypt_ecb( xtea_context *ctx,
 		 int mode,