diff --git a/sys/netinet6/udp6_usrreq.c b/sys/netinet6/udp6_usrreq.c
index e39db6c4810..375c00d0a3e 100644
--- a/sys/netinet6/udp6_usrreq.c
+++ b/sys/netinet6/udp6_usrreq.c
@@ -788,7 +788,7 @@ udp6_output(struct inpcb *inp, struct mbuf *m, struct sockaddr *addr6,
 	 * for UDP and IP6 headers.
 	 */
 	M_PREPEND(m, hlen + sizeof(struct udphdr), M_NOWAIT);
-	if (m == 0) {
+	if (m == NULL) {
 		error = ENOBUFS;
 		goto release;
 	}