diff --git a/sys/netinet/ip_mroute.c b/sys/netinet/ip_mroute.c
index 39c71b06c06..f074fea9b0b 100644
--- a/sys/netinet/ip_mroute.c
+++ b/sys/netinet/ip_mroute.c
@@ -1025,6 +1025,8 @@ expire_mfc(struct mfc *rt)
 {
 	struct rtdetq *rte, *nrte;
 
+	MFC_LOCK_ASSERT();
+
 	free_bw_list(rt->mfc_bw_meter);
 
 	TAILQ_FOREACH_SAFE(rte, &rt->mfc_stall, rte_link, nrte) {