diff --git a/library/cipher.c b/library/cipher.c
index d0000b2..f7f3d1a 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -546,7 +546,7 @@
 
     padding_len = input[input_len - 1];
 
-    if( padding_len > input_len )
+    if( padding_len > input_len || padding_len == 0 )
         return POLARSSL_ERR_CIPHER_INVALID_PADDING;
 
     for( i = input_len - padding_len; i < input_len; i++ )