--- sys/netinet/in_mcast.c.orig	2009-09-30 16:43:35.000000000 +0000
+++ sys/netinet/in_mcast.c	2009-09-30 17:04:59.000000000 +0000
@@ -2010,5 +2010,5 @@
 			 * is atomic with allocation of a membership.
 			 */
-			error = EINVAL;
+			error = EADDRINUSE;
 			goto out_inp_locked;
 		}