diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 201347b4e127..b41e231a669b 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -961,6 +961,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
 		ip_rt_put(rt);
 		goto tx_error;
 	}
+	iph6 = ipv6_hdr(skb);
 
 	if (df) {
 		mtu = dst4_mtu(&rt->dst) - t_hlen;