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,