diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 5084333b5ab6..592c73962723 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1788,12 +1788,12 @@ bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb)
 
 	__skb_pull(skb, hdrlen);
 	if (skb_try_coalesce(tail, skb, &fragstolen, &delta)) {
-		thtail->window = th->window;
-
 		TCP_SKB_CB(tail)->end_seq = TCP_SKB_CB(skb)->end_seq;
 
-		if (after(TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(tail)->ack_seq))
+		if (likely(!before(TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(tail)->ack_seq))) {
 			TCP_SKB_CB(tail)->ack_seq = TCP_SKB_CB(skb)->ack_seq;
+			thtail->window = th->window;
+		}
 
 		/* We have to update both TCP_SKB_CB(tail)->tcp_flags and
 		 * thtail->fin, so that the fast path in tcp_rcv_established()