diff --git a/pkg/tcpip/transport/tcp/rack.go b/pkg/tcpip/transport/tcp/rack.go
index 66ea6e5b0..35e6cc725 100644
--- a/pkg/tcpip/transport/tcp/rack.go
+++ b/pkg/tcpip/transport/tcp/rack.go
@@ -357,11 +357,13 @@ func (rc *rackControl) detectLoss(rcvTime tcpip.MonotonicTime) int {
 	var timeout time.Duration
 	numLost := 0
 	for seg := rc.snd.writeList.Front(); seg != nil && seg.xmitCount != 0; seg = seg.Next() {
-		if rc.snd.ep.scoreboard.IsSACKED(seg.sackBlock()) {
+		// xmitCount can be 0 for packets that are broken up for PMTUD.
+		// The initial transmission "doesn't count" WRT loss detection.
+		if rc.snd.ep.scoreboard.IsSACKED(seg.sackBlock()) || seg.xmitCount == 0 {
 			continue
 		}
 
-		if seg.lost && seg.xmitCount == 1 {
+		if seg.lost && seg.xmitCount > 1 {
 			numLost++
 			continue
 		}
diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index 5dccf81d1..4e51d8b03 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -342,10 +342,16 @@ func (s *sender) updateMaxPayloadSize(mtu, count int) {
 			break
 		}
 
-		if nextSeg == s.writeNext && seg.payloadSize() > m {
-			// We found a segment exceeding the MTU. Rewind
-			// writeNext and try to retransmit it.
-			nextSeg = seg
+		if seg.payloadSize() > m {
+			// xmitCount is used for loss detection, but
+			// retransmission doesn't indicate congestion here,
+			// it's just PMTUD.
+			seg.xmitCount = 0
+			if nextSeg == s.writeNext {
+				// We found a segment exceeding the MTU. Rewind
+				// writeNext and try to retransmit it.
+				nextSeg = seg
+			}
 		}
 
 		if s.ep.SACKPermitted && s.ep.scoreboard.IsSACKED(seg.sackBlock()) {
diff --git a/pkg/tcpip/transport/tcp/test/e2e/tcp_test.go b/pkg/tcpip/transport/tcp/test/e2e/tcp_test.go
index 9dcb8de85..5981be60f 100644
--- a/pkg/tcpip/transport/tcp/test/e2e/tcp_test.go
+++ b/pkg/tcpip/transport/tcp/test/e2e/tcp_test.go
@@ -5739,6 +5739,7 @@ func TestPathMTUDiscovery(t *testing.T) {
 			}
 			checker.IPv4(t, p,
 				checker.PayloadLen(size+header.TCPMinimumSize),
+				checker.FragmentFlags(header.IPv4FlagDontFragment),
 				checker.TCP(
 					checker.DstPort(context.TestPort),
 					checker.TCPSeqNum(seqNum),