diff --git a/include/polarssl/cipher.h b/include/polarssl/cipher.h
index b520d92..cf149f6 100644
--- a/include/polarssl/cipher.h
+++ b/include/polarssl/cipher.h
@@ -105,9 +105,10 @@
 } cipher_mode_t;
 
 typedef enum {
-    POLARSSL_PADDING_PKCS7 = 0,     /**< PKCS7 padding (default) */
-    POLARSSL_PADDING_ONE_AND_ZEROS, /**< ISO/IEC 7816-4 padding  */
-    POLARSSL_PADDING_ZEROS_AND_LEN, /**< ANSI X.923 padding      */
+    POLARSSL_PADDING_PKCS7 = 0,     /**< PKCS7 padding (default)        */
+    POLARSSL_PADDING_ONE_AND_ZEROS, /**< ISO/IEC 7816-4 padding         */
+    POLARSSL_PADDING_ZEROS_AND_LEN, /**< ANSI X.923 padding             */
+    POLARSSL_PADDING_ZEROS,         /**< zero padding (not reversible!) */
 } cipher_padding_t;
 
 typedef enum {