diff --git a/sys/netinet/in_mcast.c b/sys/netinet/in_mcast.c
--- a/sys/netinet/in_mcast.c
+++ b/sys/netinet/in_mcast.c
@@ -1180,6 +1180,7 @@
 		free(ims, M_IPMSOURCE);
 		inm->inm_nsrc--;
 	}
+	mbufq_drain(&inm->inm_scq);
 }
 
 /*