diff --git a/channels.c b/channels.c
index 1052b80..9efe89c 100644
--- a/channels.c
+++ b/channels.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.c,v 1.330 2014/02/15 23:05:36 djm Exp $ */
+/* $OpenBSD: channels.c,v 1.331 2014/02/26 20:29:29 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1072,6 +1072,9 @@
 	buffer_get(&c->input, (char *)&s4_req.dest_addr, 4);
 	have = buffer_len(&c->input);
 	p = buffer_ptr(&c->input);
+	if (memchr(p, '\0', have) == NULL)
+		fatal("channel %d: decode socks4: user not nul terminated",
+		    c->self);
 	len = strlen(p);
 	debug2("channel %d: decode socks4: user %s/%d", c->self, p, len);
 	len++;					/* trailing '\0' */