diff --git a/internal/ackhandler/sent_packet_handler.go b/internal/ackhandler/sent_packet_handler.go
index 83d75d8b..8dead2a9 100644
--- a/internal/ackhandler/sent_packet_handler.go
+++ b/internal/ackhandler/sent_packet_handler.go
@@ -329,7 +329,7 @@ func (h *sentPacketHandler) setLossDetectionTimer() {
 	}
 
 	// PTO alarm
-	h.alarm = h.lastSentAckElicitingPacketTime.Add(h.rttStats.PTO() << h.ptoCount)
+	h.alarm = h.lastSentAckElicitingPacketTime.Add(h.rttStats.PTO(true) << h.ptoCount)
 }
 
 func (h *sentPacketHandler) detectLostPackets(
diff --git a/internal/congestion/rtt_stats.go b/internal/congestion/rtt_stats.go
index 0b17fc10..9ae42706 100644
--- a/internal/congestion/rtt_stats.go
+++ b/internal/congestion/rtt_stats.go
@@ -46,13 +46,19 @@ func (r *RTTStats) SmoothedRTT() time.Duration { return r.smoothedRTT }
 // MeanDeviation gets the mean deviation
 func (r *RTTStats) MeanDeviation() time.Duration { return r.meanDeviation }
 
+// MaxAckDelay gets the max_ack_delay advertized by the peer
 func (r *RTTStats) MaxAckDelay() time.Duration { return r.maxAckDelay }
 
-func (r *RTTStats) PTO() time.Duration {
+// PTO gets the probe timeout duration.
+func (r *RTTStats) PTO(includeMaxAckDelay bool) time.Duration {
 	if r.SmoothedRTT() == 0 {
 		return 2 * defaultInitialRTT
 	}
-	return r.SmoothedRTT() + utils.MaxDuration(4*r.MeanDeviation(), protocol.TimerGranularity) + r.MaxAckDelay()
+	pto := r.SmoothedRTT() + utils.MaxDuration(4*r.MeanDeviation(), protocol.TimerGranularity)
+	if includeMaxAckDelay {
+		pto += r.MaxAckDelay()
+	}
+	return pto
 }
 
 // UpdateRTT updates the RTT based on a new sample.
diff --git a/internal/congestion/rtt_stats_test.go b/internal/congestion/rtt_stats_test.go
index c899dde0..fe722281 100644
--- a/internal/congestion/rtt_stats_test.go
+++ b/internal/congestion/rtt_stats_test.go
@@ -66,13 +66,14 @@ var _ = Describe("RTT stats", func() {
 		rttStats.UpdateRTT(rtt, 0, time.Time{})
 		Expect(rttStats.SmoothedRTT()).To(Equal(rtt))
 		Expect(rttStats.MeanDeviation()).To(Equal(rtt / 2))
-		Expect(rttStats.PTO()).To(Equal(rtt + 4*(rtt/2) + maxAckDelay))
+		Expect(rttStats.PTO(false)).To(Equal(rtt + 4*(rtt/2)))
+		Expect(rttStats.PTO(true)).To(Equal(rtt + 4*(rtt/2) + maxAckDelay))
 	})
 
 	It("uses the granularity for computing the PTO for short RTTs", func() {
 		rtt := time.Microsecond
 		rttStats.UpdateRTT(rtt, 0, time.Time{})
-		Expect(rttStats.PTO()).To(Equal(rtt + protocol.TimerGranularity))
+		Expect(rttStats.PTO(true)).To(Equal(rtt + protocol.TimerGranularity))
 	})
 
 	It("ExpireSmoothedMetrics", func() {
diff --git a/internal/handshake/updatable_aead.go b/internal/handshake/updatable_aead.go
index 2444bc50..5cc58511 100644
--- a/internal/handshake/updatable_aead.go
+++ b/internal/handshake/updatable_aead.go
@@ -99,7 +99,7 @@ func (a *updatableAEAD) rollKeys(now time.Time) {
 	a.numRcvdWithCurrentKey = 0
 	a.numSentWithCurrentKey = 0
 	a.prevRcvAEAD = a.rcvAEAD
-	a.prevRcvAEADExpiry = now.Add(3 * a.rttStats.PTO())
+	a.prevRcvAEADExpiry = now.Add(3 * a.rttStats.PTO(true))
 	a.rcvAEAD = a.nextRcvAEAD
 	a.sendAEAD = a.nextSendAEAD
 
diff --git a/internal/handshake/updatable_aead_test.go b/internal/handshake/updatable_aead_test.go
index 51000a44..54d071de 100644
--- a/internal/handshake/updatable_aead_test.go
+++ b/internal/handshake/updatable_aead_test.go
@@ -151,7 +151,7 @@ var _ = Describe("Updatable AEAD", func() {
 						It("drops keys 3 PTOs after a key update", func() {
 							now := time.Now()
 							rttStats.UpdateRTT(10*time.Millisecond, 0, now)
-							pto := rttStats.PTO()
+							pto := rttStats.PTO(true)
 							encrypted01 := client.Seal(nil, msg, 0x42, ad)
 							encrypted02 := client.Seal(nil, msg, 0x43, ad)
 							// receive the first packet with key phase 0