diff --git a/sys/netinet/in_mcast.c b/sys/netinet/in_mcast.c
index 3dc4fa27168..b0be48b6543 100644
--- a/sys/netinet/in_mcast.c
+++ b/sys/netinet/in_mcast.c
@@ -2601,6 +2601,7 @@ inp_set_source_filters(struct inpcb *inp, struct sockopt *sopt)
 		error = copyin(msfr.msfr_srcs, kss,
 		    sizeof(struct sockaddr_storage) * msfr.msfr_nsrcs);
 		if (error) {
+			IN_MULTI_UNLOCK();
 			free(kss, M_TEMP);
 			return (error);
 		}