diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index c69f1c871922..b9e8d2b759e9 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -384,6 +384,8 @@ static inline unsigned int ip6_dst_mtu_maybe_forward(const struct dst_entry *dst
 	rcu_read_unlock();
 
 out:
+	mtu = min_t(unsigned int, mtu, IP6_MAX_MTU);
+
 	return mtu - lwtunnel_headroom(dst->lwtstate, mtu);
 }