--- sys/netinet/in_mcast.c.orig	2009-08-03 08:13:06.000000000 +0000
+++ sys/netinet/in_mcast.c	2009-09-09 15:01:24.000000000 +0000
@@ -2024,6 +2050,9 @@
 			error = ENOMEM;
 			goto out_imo_free;
 		}
+	} else if (is_new) {
+		/* Old style ASM filter mode is always exclude */
+		imf_init(imf, MCAST_UNDEFINED, MCAST_EXCLUDE);
 	}
 
 	/*