diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 73c5b4189866..3fd0e215324d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -107,7 +107,8 @@ int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
 #define FLAG_TS_PROGRESS	0x40000 /* Positive timestamp delta */
 
 #define FLAG_ACKED		(FLAG_DATA_ACKED|FLAG_SYN_ACKED)
-#define FLAG_NOT_DUP		(FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
+#define FLAG_NOT_DUP		(FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED|	\
+				 FLAG_SND_UNA_ADVANCED)
 #define FLAG_CA_ALERT		(FLAG_DATA_SACKED|FLAG_ECE|FLAG_DSACKING_ACK)
 #define FLAG_FORWARD_PROGRESS	(FLAG_ACKED|FLAG_DATA_SACKED)
 
@@ -3986,11 +3987,11 @@ static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32
 		nwin <<= tp->rx_opt.snd_wscale;
 
 	if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
-		flag |= FLAG_WIN_UPDATE;
 		tcp_update_wl(tp, ack_seq);
 
 		if (tp->snd_wnd != nwin) {
 			tp->snd_wnd = nwin;
+			flag |= FLAG_WIN_UPDATE;
 
 			/* Note, it is the only place, where
 			 * fast path is recovered for sending TCP.
@@ -4381,7 +4382,6 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 		 */
 		tcp_update_wl(tp, ack_seq);
 		tcp_snd_una_update(tp, ack);
-		flag |= FLAG_WIN_UPDATE;
 
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPACKS);
 	} else {
diff --git a/tools/testing/selftests/net/packetdrill/tcp_bidir_fast_retransmit_nosack.pkt b/tools/testing/selftests/net/packetdrill/tcp_bidir_fast_retransmit_nosack.pkt
new file mode 100644
index 000000000000..5c66b7171d22
--- /dev/null
+++ b/tools/testing/selftests/net/packetdrill/tcp_bidir_fast_retransmit_nosack.pkt
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Verify that non-SACK connections properly detect duplicate acks when mixed
+// with other data segments from peer.
+
+`./defaults.sh`
+
+    0     socket(..., SOCK_STREAM, IPPROTO_TCP) = 4
+   +0...0 connect(4, ..., ...) = 0
+
+   // Three-way handshake, SACK not supported by peer
+   +0 > S  0:0(0) <mss 1460,sackOK,TS val 0 ecr 0,nop,wscale 8>
+   +0 < S. 0:0(0) ack 1 win 65535 <mss 1000>
+   +0 > .  1:1(0) ack 1
+
+   // Send 1000 bytes, peer acks everything
+   +0 send(4, ..., 1000, 0) = 1000
+   +0 > P. 1:1001(1000) ack 1
+   +0 < .  1:1(0) ack 1001 win 65535
+
+   // Send 4000 more bytes
+   +0 send(4, ..., 4000, 0) = 4000
+   +0 > P. 1001:5001(4000) ack 1
+
+   // Receive first dup-ack (considering segment 1001-2001 was lost)
+   +0 < .  1:1(0) ack 1001 win 65535
+
+   // Receive unrelated data segment from peer and ack it
+   +0 < P. 1:11(10) ack 1001 win 65535
+   +0 > .  5001:5001(0) ack 11
+
+   // Receive second dup-ack
+   +0 < .  11:11(0) ack 1001 win 65535
+
+   // Receive another data segment from peer and ack it
+   +0 < P. 11:21(10) ack 1001 win 65535
+   +0 > .  5001:5001(0) ack 21
+
+   // Receive third dup-ack, which should trigger fast retransmit (without
+   // waiting for RTO)
+   +0 < .  21:21(0) ack 1001 win 65535
+   +0 > .  1001:2001(1000) ack 21