Index: b/cipher/md.c
===================================================================
--- b/cipher/md.c
+++ b/cipher/md.c
@@ -1264,7 +1264,7 @@
 	GcryDigestEntry *r;
 	int algo;
 
-	if ( !buffer || (nbytes && (*nbytes != sizeof (int))))
+	if ( !buffer || !nbytes || (*nbytes != sizeof (int)))
 	  err = GPG_ERR_INV_ARG;
 	else
 	  {