diff --git a/sys/netinet6/ip6_mroute.c b/sys/netinet6/ip6_mroute.c
--- a/sys/netinet6/ip6_mroute.c
+++ b/sys/netinet6/ip6_mroute.c
@@ -748,6 +748,8 @@
 
 			rt->mf6c_origin     = mfccp->mf6cc_origin;
 			rt->mf6c_mcastgrp   = mfccp->mf6cc_mcastgrp;
+			if (mfccp->mf6cc_parent >= nummifs)
+				rt->mf6c_parent = 0;
 			rt->mf6c_parent     = mfccp->mf6cc_parent;
 			rt->mf6c_ifset	    = mfccp->mf6cc_ifset;
 			/* initialize pkt counters per src-grp */