diff --git a/sys/netinet6/in6.c b/sys/netinet6/in6.c
index 5c1563c7e1b..2b022ba27d4 100644
--- a/sys/netinet6/in6.c
+++ b/sys/netinet6/in6.c
@@ -2432,6 +2432,8 @@ in6_domifattach(struct ifnet *ifp)
 int
 in6_domifmtu(struct ifnet *ifp)
 {
+	if (ifp->if_afdata[AF_INET6] == NULL)
+		return ifp->if_mtu;
 
 	return (IN6_LINKMTU(ifp));
 }
diff --git a/sys/netinet6/nd6.c b/sys/netinet6/nd6.c
index a79922b8353..5e9a067fd4f 100644
--- a/sys/netinet6/nd6.c
+++ b/sys/netinet6/nd6.c
@@ -285,6 +285,8 @@ nd6_ifdetach(struct nd_ifinfo *nd)
 void
 nd6_setmtu(struct ifnet *ifp)
 {
+	if (ifp->if_afdata[AF_INET6] == NULL)
+		return;
 
 	nd6_setmtu0(ifp, ND_IFINFO(ifp));
 }