--- sys/netinet/in_mcast.c.orig	2009-08-03 08:13:06.000000000 +0000
+++ sys/netinet/in_mcast.c	2009-09-09 01:35:06.000000000 +0000
@@ -2139,6 +2143,9 @@
 		}
 
-		if (!in_nullhost(gsa->sin.sin_addr))
+		if (!in_nullhost(gsa->sin.sin_addr)) {
 			INADDR_TO_IFP(mreqs.imr_interface, ifp);
+			if (ifp == NULL)
+				return (EADDRNOTAVAIL);
+		}
 
 		CTR3(KTR_IGMPV3, "%s: imr_interface = %s, ifp = %p",