diff --git a/quiche/common/quiche_feature_flags_list.h b/quiche/common/quiche_feature_flags_list.h
index 1ba8145..e427089 100755
--- a/quiche/common/quiche_feature_flags_list.h
+++ b/quiche/common/quiche_feature_flags_list.h
@@ -19,7 +19,6 @@
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_clear_body_manager_along_with_sequencer, true, true, "If true, QuicSpdyStream::StopReading always clears BodyManager along with the SequenceBuffer.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_clear_packet_on_serialization_failure, false, false, "If true, clear QuicPacketCreator state when serialization failure.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_client_check_blockage_before_on_can_write, false, false, "If true, quic clients will only call OnCanWrite() upon write events if the writer is unblocked.")
-QUICHE_FLAG(bool, quiche_reloadable_flag_quic_close_connection_on_underflow, true, true, "If true, close QUIC connections if a RESET_STREAM frame is received with a too-small final byte offset value.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_close_on_idle_timeout, false, false, "If true, closes the connection if it has exceeded the idle timeout when deciding whether to open a stream.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_conservative_bursts, false, false, "If true, set burst token to 2 in cwnd bootstrapping experiment.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_conservative_cwnd_and_pacing_gains, false, false, "If true, uses conservative cwnd gain and pacing gain when cwnd gets bootstrapped.")
diff --git a/quiche/quic/core/quic_session.cc b/quiche/quic/core/quic_session.cc
index 6f8ad27..4ff5df5 100644
--- a/quiche/quic/core/quic_session.cc
+++ b/quiche/quic/core/quic_session.cc
@@ -1329,14 +1329,11 @@
 
   QUIC_DVLOG(1) << ENDPOINT << "Received final byte offset "
                 << final_byte_offset << " for stream " << stream_id;
-  if (GetQuicReloadableFlag(quic_close_connection_on_underflow)) {
-    QUIC_RELOADABLE_FLAG_COUNT(quic_close_connection_on_underflow);
-    if (final_byte_offset < it->second) {
-      connection_->CloseConnection(
-          QUIC_FLOW_CONTROL_FINAL_SIZE_CHANGED, "Invalid final byte offset",
-          ConnectionCloseBehavior::SEND_CONNECTION_CLOSE_PACKET);
-      return;
-    }
+  if (final_byte_offset < it->second) {
+    connection_->CloseConnection(
+        QUIC_FLOW_CONTROL_FINAL_SIZE_CHANGED, "Invalid final byte offset",
+        ConnectionCloseBehavior::SEND_CONNECTION_CLOSE_PACKET);
+    return;
   }
   QuicByteCount offset_diff = final_byte_offset - it->second;
   if (flow_controller_.UpdateHighestReceivedOffset(
diff --git a/quiche/quic/core/quic_session_test.cc b/quiche/quic/core/quic_session_test.cc
index b121155..01a1b07 100644
--- a/quiche/quic/core/quic_session_test.cc
+++ b/quiche/quic/core/quic_session_test.cc
@@ -3664,15 +3664,11 @@
       /*control_frame_id=*/kInvalidControlFrameId, stream_id,
       QUIC_STREAM_CANCELLED,
       /*bytes_written=*/0);
-  if (GetQuicReloadableFlag(quic_close_connection_on_underflow)) {
-    EXPECT_CALL(
-        *connection_,
-        CloseConnection(QUIC_FLOW_CONTROL_FINAL_SIZE_CHANGED,
-                        "Invalid final byte offset",
-                        ConnectionCloseBehavior::SEND_CONNECTION_CLOSE_PACKET));
-  } else {
-    EXPECT_CALL(*connection_, CloseConnection(_, _, _)).Times(0);
-  }
+  EXPECT_CALL(
+      *connection_,
+      CloseConnection(QUIC_FLOW_CONTROL_FINAL_SIZE_CHANGED,
+                      "Invalid final byte offset",
+                      ConnectionCloseBehavior::SEND_CONNECTION_CLOSE_PACKET));
   session_.OnRstStream(malicious_rst);
 
   EXPECT_EQ(session_.flow_controller()->highest_received_byte_offset(),
@@ -3680,11 +3676,7 @@
   const QuicByteCount bytes_consumed_after =
       session_.flow_controller()->bytes_consumed();
 
-  if (GetQuicReloadableFlag(quic_close_connection_on_underflow)) {
-    EXPECT_EQ(bytes_consumed_after, kDataSize);
-  } else {
-    EXPECT_NE(bytes_consumed_after, kDataSize);
-  }
+  EXPECT_EQ(bytes_consumed_after, kDataSize);
 }
 
 }  // namespace