diff --git a/sys/netinet/udp_usrreq.c b/sys/netinet/udp_usrreq.c
index 16796996eb15..04a44348889a 100644
--- a/sys/netinet/udp_usrreq.c
+++ b/sys/netinet/udp_usrreq.c
@@ -243,6 +243,8 @@ udp_input(struct mbuf *m, int off)
 	 */
 	if (!blackhole)
 		save_ip = *ip;
+	else
+		memset(&save_ip, 0, sizeof(save_ip));
 
 	/*
 	 * Checksum extended UDP header and data.