diff --git a/quic/core/quic_sent_packet_manager.cc b/quic/core/quic_sent_packet_manager.cc
index 44b2ac4..2b52dd2 100644
--- a/quic/core/quic_sent_packet_manager.cc
+++ b/quic/core/quic_sent_packet_manager.cc
@@ -46,7 +46,8 @@
   return transmission_type == HANDSHAKE_RETRANSMISSION ||
          transmission_type == TLP_RETRANSMISSION ||
          transmission_type == PROBING_RETRANSMISSION ||
-         transmission_type == RTO_RETRANSMISSION;
+         transmission_type == RTO_RETRANSMISSION ||
+         transmission_type == PTO_RETRANSMISSION;
 }
 
 // If pacing rate is accurate, > 2 burst token is not likely to help first ACK
@@ -441,7 +442,7 @@
               !unacked_packets_.HasRetransmittableFrames(*transmission_info))
       << "transmission_type: " << TransmissionTypeToString(transmission_type);
   // Handshake packets should never be sent as probing retransmissions.
-  DCHECK(pto_enabled_ || !transmission_info->has_crypto_handshake ||
+  DCHECK(!transmission_info->has_crypto_handshake ||
          transmission_type != PROBING_RETRANSMISSION);
 
   HandleRetransmission(transmission_type, transmission_info);
@@ -727,7 +728,7 @@
   for (QuicPacketNumber retransmission : probing_packets) {
     QUIC_DVLOG(1) << ENDPOINT << "Marking " << retransmission
                   << " for probing retransmission";
-    MarkForRetransmission(retransmission, PROBING_RETRANSMISSION);
+    MarkForRetransmission(retransmission, PTO_RETRANSMISSION);
   }
   // It is possible that there is not enough outstanding data for probing.
 }
diff --git a/quic/core/quic_types.cc b/quic/core/quic_types.cc
index 6ebc4eb..5e717de 100644
--- a/quic/core/quic_types.cc
+++ b/quic/core/quic_types.cc
@@ -478,6 +478,7 @@
     RETURN_STRING_LITERAL(LOSS_RETRANSMISSION);
     RETURN_STRING_LITERAL(RTO_RETRANSMISSION);
     RETURN_STRING_LITERAL(TLP_RETRANSMISSION);
+    RETURN_STRING_LITERAL(PTO_RETRANSMISSION);
     RETURN_STRING_LITERAL(PROBING_RETRANSMISSION);
     default:
       // Some varz rely on this behavior for statistic collection.
diff --git a/quic/core/quic_types.h b/quic/core/quic_types.h
index f3299d0..60754c0 100644
--- a/quic/core/quic_types.h
+++ b/quic/core/quic_types.h
@@ -156,6 +156,7 @@
   LOSS_RETRANSMISSION,         // Retransmits due to loss detection.
   RTO_RETRANSMISSION,          // Retransmits due to retransmit time out.
   TLP_RETRANSMISSION,          // Tail loss probes.
+  PTO_RETRANSMISSION,          // Retransmission due to probe timeout.
   PROBING_RETRANSMISSION,      // Retransmission in order to probe bandwidth.
   LAST_TRANSMISSION_TYPE = PROBING_RETRANSMISSION,
 };
@@ -465,6 +466,8 @@
   TLP_RETRANSMITTED,
   // This packet has been retransmitted when RTO fires.
   RTO_RETRANSMITTED,
+  // This packet has been retransmitted when PTO fires.
+  PTO_RETRANSMITTED,
   // This packet has been retransmitted for probing purpose.
   PROBE_RETRANSMITTED,
   LAST_PACKET_STATE = PROBE_RETRANSMITTED,
diff --git a/quic/core/quic_utils.cc b/quic/core/quic_utils.cc
index 297cc8b..a6f6577 100644
--- a/quic/core/quic_utils.cc
+++ b/quic/core/quic_utils.cc
@@ -165,6 +165,7 @@
     RETURN_STRING_LITERAL(LOST);
     RETURN_STRING_LITERAL(TLP_RETRANSMITTED);
     RETURN_STRING_LITERAL(RTO_RETRANSMITTED);
+    RETURN_STRING_LITERAL(PTO_RETRANSMITTED);
     RETURN_STRING_LITERAL(PROBE_RETRANSMITTED);
   }
   return "INVALID_SENT_PACKET_STATE";
@@ -329,6 +330,8 @@
       return TLP_RETRANSMITTED;
     case RTO_RETRANSMISSION:
       return RTO_RETRANSMITTED;
+    case PTO_RETRANSMISSION:
+      return PTO_RETRANSMITTED;
     case PROBING_RETRANSMISSION:
       return PROBE_RETRANSMITTED;
     default:
diff --git a/quic/core/quic_utils_test.cc b/quic/core/quic_utils_test.cc
index 213ff38..362c766 100644
--- a/quic/core/quic_utils_test.cc
+++ b/quic/core/quic_utils_test.cc
@@ -131,6 +131,8 @@
       EXPECT_EQ(TLP_RETRANSMITTED, state);
     } else if (i == RTO_RETRANSMISSION) {
       EXPECT_EQ(RTO_RETRANSMITTED, state);
+    } else if (i == PTO_RETRANSMISSION) {
+      EXPECT_EQ(PTO_RETRANSMITTED, state);
     } else if (i == PROBING_RETRANSMISSION) {
       EXPECT_EQ(PROBE_RETRANSMITTED, state);
     } else {