diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ad787e7882f74eb9ad8519d81436d37cd4b608ec..e3ce1f56f845678e12717aa1668f79b0331ef982 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -60,6 +60,9 @@ static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
 	__skb_unlink(skb, &sk->sk_write_queue);
 	tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
 
+	if (tp->highest_sack == NULL)
+		tp->highest_sack = skb;
+
 	tp->packets_out += tcp_skb_pcount(skb);
 	if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
 		tcp_rearm_rto(sk);