diff --git a/quic/core/quic_sent_packet_manager.cc b/quic/core/quic_sent_packet_manager.cc
index d6bf700..70ae9ea 100644
--- a/quic/core/quic_sent_packet_manager.cc
+++ b/quic/core/quic_sent_packet_manager.cc
@@ -109,6 +109,7 @@
       max_probe_packets_per_pto_(2),
       consecutive_pto_count_(0),
       handshake_mode_disabled_(false),
+      forward_secure_packet_acked_(false),
       detect_spurious_losses_(GetQuicReloadableFlag(quic_detect_spurious_loss)),
       neuter_handshake_packets_once_(
           GetQuicReloadableFlag(quic_neuter_handshake_packets_once)) {
@@ -1370,6 +1371,9 @@
       return PACKETS_ACKED_IN_WRONG_PACKET_NUMBER_SPACE;
     }
     last_ack_frame_.packets.Add(acked_packet.packet_number);
+    if (info->encryption_level == ENCRYPTION_FORWARD_SECURE) {
+      forward_secure_packet_acked_ = true;
+    }
     largest_packet_peer_knows_is_acked_.UpdateMax(info->largest_acked);
     if (supports_multiple_packet_number_spaces()) {
       largest_packets_peer_knows_is_acked_[packet_number_space].UpdateMax(
diff --git a/quic/core/quic_sent_packet_manager.h b/quic/core/quic_sent_packet_manager.h
index e0adb01..eee5e01 100644
--- a/quic/core/quic_sent_packet_manager.h
+++ b/quic/core/quic_sent_packet_manager.h
@@ -413,6 +413,10 @@
 
   bool handshake_mode_disabled() const { return handshake_mode_disabled_; }
 
+  bool forward_secure_packet_acked() const {
+    return forward_secure_packet_acked_;
+  }
+
  private:
   friend class test::QuicConnectionPeer;
   friend class test::QuicSentPacketManagerPeer;
@@ -653,6 +657,10 @@
   // True if HANDSHAKE mode has been disabled.
   bool handshake_mode_disabled_;
 
+  // True if an acknowledgment has been received for a sent
+  // ENCRYPTION_FORWARD_SECURE packet.
+  bool forward_secure_packet_acked_;
+
   // Latched value of quic_detect_spurious_loss.
   const bool detect_spurious_losses_;
 
diff --git a/quic/core/quic_sent_packet_manager_test.cc b/quic/core/quic_sent_packet_manager_test.cc
index 389f5cb..c7b3cfd 100644
--- a/quic/core/quic_sent_packet_manager_test.cc
+++ b/quic/core/quic_sent_packet_manager_test.cc
@@ -3218,6 +3218,42 @@
   EXPECT_EQ(QuicTime::Zero(), manager_.GetRetransmissionTime());
 }
 
+TEST_P(QuicSentPacketManagerTest, ForwardSecurePacketAcked) {
+  EXPECT_FALSE(manager_.forward_secure_packet_acked());
+  SendDataPacket(1, ENCRYPTION_INITIAL);
+  // Ack packet 1.
+  ExpectAck(1);
+  manager_.OnAckFrameStart(QuicPacketNumber(1), QuicTime::Delta::Infinite(),
+                           clock_.Now());
+  manager_.OnAckRange(QuicPacketNumber(1), QuicPacketNumber(2));
+  EXPECT_EQ(PACKETS_NEWLY_ACKED,
+            manager_.OnAckFrameEnd(clock_.Now(), QuicPacketNumber(1),
+                                   ENCRYPTION_INITIAL));
+  EXPECT_FALSE(manager_.forward_secure_packet_acked());
+
+  SendDataPacket(2, ENCRYPTION_ZERO_RTT);
+  // Ack packet 2.
+  ExpectAck(2);
+  manager_.OnAckFrameStart(QuicPacketNumber(2), QuicTime::Delta::Infinite(),
+                           clock_.Now());
+  manager_.OnAckRange(QuicPacketNumber(2), QuicPacketNumber(3));
+  EXPECT_EQ(PACKETS_NEWLY_ACKED,
+            manager_.OnAckFrameEnd(clock_.Now(), QuicPacketNumber(2),
+                                   ENCRYPTION_FORWARD_SECURE));
+  EXPECT_FALSE(manager_.forward_secure_packet_acked());
+
+  SendDataPacket(3, ENCRYPTION_FORWARD_SECURE);
+  // Ack packet 3.
+  ExpectAck(3);
+  manager_.OnAckFrameStart(QuicPacketNumber(3), QuicTime::Delta::Infinite(),
+                           clock_.Now());
+  manager_.OnAckRange(QuicPacketNumber(3), QuicPacketNumber(4));
+  EXPECT_EQ(PACKETS_NEWLY_ACKED,
+            manager_.OnAckFrameEnd(clock_.Now(), QuicPacketNumber(3),
+                                   ENCRYPTION_FORWARD_SECURE));
+  EXPECT_TRUE(manager_.forward_secure_packet_acked());
+}
+
 }  // namespace
 }  // namespace test
 }  // namespace quic