diff --git a/include/net/tcp.h b/include/net/tcp.h
index 33599d17522d..e6d0002a1b0b 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1771,12 +1771,12 @@ static inline void tcp_highest_sack_reset(struct sock *sk)
 	tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
 }
 
-/* Called when old skb is about to be deleted (to be combined with new skb) */
-static inline void tcp_highest_sack_combine(struct sock *sk,
+/* Called when old skb is about to be deleted and replaced by new skb */
+static inline void tcp_highest_sack_replace(struct sock *sk,
 					    struct sk_buff *old,
 					    struct sk_buff *new)
 {
-	if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
+	if (old == tcp_highest_sack(sk))
 		tcp_sk(sk)->highest_sack = new;
 }
 
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ae60dd3faed0..823003eef3a2 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2062,6 +2062,7 @@ static int tcp_mtu_probe(struct sock *sk)
 	nskb->ip_summed = skb->ip_summed;
 
 	tcp_insert_write_queue_before(nskb, skb, sk);
+	tcp_highest_sack_replace(sk, skb, nskb);
 
 	len = 0;
 	tcp_for_write_queue_from_safe(skb, next, sk) {
@@ -2665,7 +2666,7 @@ static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
 		else if (!skb_shift(skb, next_skb, next_skb_size))
 			return false;
 	}
-	tcp_highest_sack_combine(sk, next_skb, skb);
+	tcp_highest_sack_replace(sk, next_skb, skb);
 
 	tcp_unlink_write_queue(next_skb, sk);