diff --git a/include/polarssl/aes.h b/include/polarssl/aes.h
index 83fe8f2f6..dc971c19e 100644
--- a/include/polarssl/aes.h
+++ b/include/polarssl/aes.h
@@ -73,6 +73,8 @@ void aes_crypt_ecb( aes_context *ctx,
 
 /**
  * \brief          AES-CBC buffer encryption/decryption
+ *                 Length should be a multiple of the block
+ *                 size (16 bytes)
  *
  * \param ctx      AES context
  * \param mode     AES_ENCRYPT or AES_DECRYPT
@@ -89,7 +91,7 @@ void aes_crypt_cbc( aes_context *ctx,
                     unsigned char *output );
 
 /**
- * \brief          AES-CFB128 buffer encryption/decryption
+ * \brief          AES-CFB128 buffer encryption/decryption.
  *
  * \param ctx      AES context
  * \param mode     AES_ENCRYPT or AES_DECRYPT
diff --git a/include/polarssl/camellia.h b/include/polarssl/camellia.h
index 1b144e790..9bf5e91f5 100644
--- a/include/polarssl/camellia.h
+++ b/include/polarssl/camellia.h
@@ -72,6 +72,8 @@ void camellia_crypt_ecb( camellia_context *ctx,
 
 /**
  * \brief          CAMELLIA-CBC buffer encryption/decryption
+ *                 Length should be a multiple of the block
+ *                 size (16 bytes)
  *
  * \param ctx      CAMELLIA context
  * \param mode     CAMELLIA_ENCRYPT or CAMELLIA_DECRYPT