diff --git a/quic/core/crypto/transport_parameters.cc b/quic/core/crypto/transport_parameters.cc
index dcd2fc9..fec6cc5 100644
--- a/quic/core/crypto/transport_parameters.cc
+++ b/quic/core/crypto/transport_parameters.cc
@@ -156,12 +156,13 @@
     case TransportParameters::kMaxDatagramFrameSize:
     case TransportParameters::kInitialRoundTripTime:
     case TransportParameters::kGoogleConnectionOptions:
-    case TransportParameters::kGoogleKeyUpdateNotYetSupported:
     case TransportParameters::kGoogleQuicVersion:
     case TransportParameters::kMinAckDelay:
       return true;
     case TransportParameters::kGoogleUserAgentId:
       return !GetQuicReloadableFlag(quic_ignore_user_agent_transport_parameter);
+    case TransportParameters::kGoogleKeyUpdateNotYetSupported:
+      return !GetQuicReloadableFlag(quic_ignore_key_update_not_yet_supported);
   }
   return false;
 }
@@ -1351,6 +1352,24 @@
         out->user_agent_id = std::string(value_reader.ReadRemainingPayload());
         break;
       case TransportParameters::kGoogleKeyUpdateNotYetSupported:
+        if (GetQuicReloadableFlag(quic_ignore_key_update_not_yet_supported)) {
+          QUIC_RELOADABLE_FLAG_COUNT_N(quic_ignore_key_update_not_yet_supported,
+                                       1, 2);
+          QUIC_CODE_COUNT(quic_ignore_key_update_not_yet_supported_ignored);
+          // This is a copy of the default switch statement below.
+          // TODO(dschinazi) remove this case entirely when deprecating the
+          // quic_ignore_key_update_not_yet_supported flag.
+          if (out->custom_parameters.find(param_id) !=
+              out->custom_parameters.end()) {
+            *error_details = "Received a second unknown parameter" +
+                             TransportParameterIdToString(param_id);
+            return false;
+          }
+          out->custom_parameters[param_id] =
+              std::string(value_reader.ReadRemainingPayload());
+          break;
+        }
+        QUIC_CODE_COUNT(quic_ignore_key_update_not_yet_supported_received);
         if (out->key_update_not_yet_supported) {
           *error_details = "Received a second key_update_not_yet_supported";
           return false;
diff --git a/quic/core/crypto/transport_parameters_test.cc b/quic/core/crypto/transport_parameters_test.cc
index a758d81..05ada68 100644
--- a/quic/core/crypto/transport_parameters_test.cc
+++ b/quic/core/crypto/transport_parameters_test.cc
@@ -285,7 +285,9 @@
   if (!GetQuicReloadableFlag(quic_ignore_user_agent_transport_parameter)) {
     orig_params.user_agent_id = CreateFakeUserAgentId();
   }
-  orig_params.key_update_not_yet_supported = kFakeKeyUpdateNotYetSupported;
+  if (!GetQuicReloadableFlag(quic_ignore_key_update_not_yet_supported)) {
+    orig_params.key_update_not_yet_supported = kFakeKeyUpdateNotYetSupported;
+  }
   orig_params.custom_parameters[kCustomParameter1] = kCustomParameter1Value;
   orig_params.custom_parameters[kCustomParameter2] = kCustomParameter2Value;
 
@@ -589,7 +591,9 @@
   } else {
     EXPECT_FALSE(new_params.user_agent_id.has_value());
   }
-  EXPECT_TRUE(new_params.key_update_not_yet_supported);
+  if (!GetQuicReloadableFlag(quic_ignore_key_update_not_yet_supported)) {
+    EXPECT_TRUE(new_params.key_update_not_yet_supported);
+  }
 }
 
 TEST_P(TransportParametersTest,
@@ -847,7 +851,9 @@
   EXPECT_EQ(CreateFakeGoogleConnectionOptions(),
             new_params.google_connection_options.value());
   EXPECT_FALSE(new_params.user_agent_id.has_value());
-  EXPECT_TRUE(new_params.key_update_not_yet_supported);
+  if (!GetQuicReloadableFlag(quic_ignore_key_update_not_yet_supported)) {
+    EXPECT_TRUE(new_params.key_update_not_yet_supported);
+  }
 }
 
 TEST_P(TransportParametersTest, ParseServerParametersRepeated) {
diff --git a/quic/core/quic_flags_list.h b/quic/core/quic_flags_list.h
index b40bd6c..3416be7 100644
--- a/quic/core/quic_flags_list.h
+++ b/quic/core/quic_flags_list.h
@@ -121,6 +121,8 @@
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_match_ietf_reset_code, false)
 // When the flag is true, exit STARTUP after the same number of loss events as PROBE_UP.
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_bbr2_startup_probe_up_loss_events, true)
+// When true, QUIC server will ignore received key_update_not_yet_supported transport parameter.
+QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_ignore_key_update_not_yet_supported, false)
 // When true, QUIC server will ignore received user agent transport parameter and rely on getting that information from HTTP headers.
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_ignore_user_agent_transport_parameter, false)
 // When true, QuicDispatcher will silently drop incoming packets whose UDP source port is on the blocklist.
diff --git a/quic/core/tls_server_handshaker.cc b/quic/core/tls_server_handshaker.cc
index 4e47a63..fba927f 100644
--- a/quic/core/tls_server_handshaker.cc
+++ b/quic/core/tls_server_handshaker.cc
@@ -474,17 +474,22 @@
   // Notify QuicConnectionDebugVisitor.
   session()->connection()->OnTransportParametersReceived(client_params);
 
-  // Chrome clients before 86.0.4233.0 did not send the
-  // key_update_not_yet_supported transport parameter, but they did send a
-  // Google-internal transport parameter with identifier 0x4751. We treat
-  // reception of 0x4751 as having received key_update_not_yet_supported to
-  // ensure we do not use key updates with those older clients.
-  // TODO(dschinazi) remove this workaround once all of our QUIC+TLS Finch
-  // experiments have a min_version greater than 86.0.4233.0.
-  if (client_params.custom_parameters.find(
-          static_cast<TransportParameters::TransportParameterId>(0x4751)) !=
-      client_params.custom_parameters.end()) {
-    client_params.key_update_not_yet_supported = true;
+  if (GetQuicReloadableFlag(quic_ignore_key_update_not_yet_supported)) {
+    QUIC_RELOADABLE_FLAG_COUNT_N(quic_ignore_key_update_not_yet_supported, 2,
+                                 2);
+  } else {
+    // Chrome clients before 86.0.4233.0 did not send the
+    // key_update_not_yet_supported transport parameter, but they did send a
+    // Google-internal transport parameter with identifier 0x4751. We treat
+    // reception of 0x4751 as having received key_update_not_yet_supported to
+    // ensure we do not use key updates with those older clients.
+    // TODO(dschinazi) remove this workaround once all of our QUIC+TLS Finch
+    // experiments have a min_version greater than 86.0.4233.0.
+    if (client_params.custom_parameters.find(
+            static_cast<TransportParameters::TransportParameterId>(0x4751)) !=
+        client_params.custom_parameters.end()) {
+      client_params.key_update_not_yet_supported = true;
+    }
   }
 
   // When interoperating with non-Google implementations that do not send