diff --git a/ssh-rsa.c b/ssh-rsa.c
index 53d44d1..a6db2a0 100644
--- a/ssh-rsa.c
+++ b/ssh-rsa.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-rsa.c,v 1.58 2015/12/11 04:21:12 mmcc Exp $ */
+/* $OpenBSD: ssh-rsa.c,v 1.59 2016/04/21 06:08:02 djm Exp $ */
 /*
  * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
  *
@@ -172,7 +172,8 @@
 
 	if (key == NULL || key->rsa == NULL ||
 	    sshkey_type_plain(key->type) != KEY_RSA ||
-	    BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
+	    BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE ||
+	    sig == NULL || siglen == 0)
 		return SSH_ERR_INVALID_ARGUMENT;
 
 	if ((b = sshbuf_from(sig, siglen)) == NULL)