diff --git a/quic/core/quic_sent_packet_manager.cc b/quic/core/quic_sent_packet_manager.cc
index ff73abf..44b2ac4 100644
--- a/quic/core/quic_sent_packet_manager.cc
+++ b/quic/core/quic_sent_packet_manager.cc
@@ -877,14 +877,6 @@
       return std::max(tlp_time, rto_time);
     }
     case PTO_MODE: {
-      if (!unacked_packets().simple_inflight_time() &&
-          handshake_mode_disabled_ && !handshake_confirmed_ &&
-          !unacked_packets_.HasInFlightPackets()) {
-        DCHECK_EQ(Perspective::IS_CLIENT, unacked_packets_.perspective());
-        return std::max(clock_->ApproximateNow(),
-                        unacked_packets_.GetLastCryptoPacketSentTime() +
-                            GetProbeTimeoutDelay());
-      }
       // Ensure PTO never gets set to a time in the past.
       return std::max(clock_->ApproximateNow(),
                       unacked_packets_.GetLastInFlightPacketSentTime() +
diff --git a/quic/core/quic_unacked_packet_map.cc b/quic/core/quic_unacked_packet_map.cc
index c652c8c..a4497c3 100644
--- a/quic/core/quic_unacked_packet_map.cc
+++ b/quic/core/quic_unacked_packet_map.cc
@@ -31,12 +31,7 @@
       last_inflight_packet_sent_time_(QuicTime::Zero()),
       last_crypto_packet_sent_time_(QuicTime::Zero()),
       session_notifier_(nullptr),
-      supports_multiple_packet_number_spaces_(false),
-      simple_inflight_time_(GetQuicReloadableFlag(quic_simple_inflight_time)) {
-  if (simple_inflight_time_) {
-    QUIC_RELOADABLE_FLAG_COUNT(quic_simple_inflight_time);
-  }
-}
+      supports_multiple_packet_number_spaces_(false) {}
 
 QuicUnackedPacketMap::~QuicUnackedPacketMap() {
   for (QuicTransmissionInfo& transmission_info : unacked_packets_) {
@@ -224,20 +219,7 @@
 }
 
 QuicTime QuicUnackedPacketMap::GetLastInFlightPacketSentTime() const {
-  if (simple_inflight_time_) {
-    return last_inflight_packet_sent_time_;
-  }
-  auto it = unacked_packets_.rbegin();
-  while (it != unacked_packets_.rend()) {
-    if (it->in_flight) {
-      QUIC_BUG_IF(it->sent_time == QuicTime::Zero())
-          << "Sent time can never be zero for a packet in flight.";
-      return it->sent_time;
-    }
-    ++it;
-  }
-  QUIC_BUG << "GetLastPacketSentTime requires in flight packets.";
-  return QuicTime::Zero();
+  return last_inflight_packet_sent_time_;
 }
 
 QuicTime QuicUnackedPacketMap::GetLastCryptoPacketSentTime() const {
diff --git a/quic/core/quic_unacked_packet_map.h b/quic/core/quic_unacked_packet_map.h
index e079bb8..6b390b7 100644
--- a/quic/core/quic_unacked_packet_map.h
+++ b/quic/core/quic_unacked_packet_map.h
@@ -211,8 +211,6 @@
     return supports_multiple_packet_number_spaces_;
   }
 
-  bool simple_inflight_time() const { return simple_inflight_time_; }
-
  private:
   friend class test::QuicUnackedPacketMapPeer;