diff --git a/quiche/common/quiche_feature_flags_list.h b/quiche/common/quiche_feature_flags_list.h
index de1359e..dcce399 100755
--- a/quiche/common/quiche_feature_flags_list.h
+++ b/quiche/common/quiche_feature_flags_list.h
@@ -35,6 +35,7 @@
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_disable_version_rfcv1, false, false, "If true, disable QUIC version h3 (RFCv1).")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_discard_initial_packet_with_key_dropped, false, true, "If true, discard INITIAL packet if the key has been dropped.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_disconnect_early_exit, false, false, "If true, does not update ack state if the connection has been closed.")
+QUICHE_FLAG(bool, quiche_reloadable_flag_quic_enable_5aff_connection_option, true, true, "If true, allows QUIC's 5AFF connection option to increase the amplication factor to 5.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_enable_disable_resumption, true, true, "If true, disable resumption when receiving NRES connection option.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_enable_mtu_discovery_at_server, false, false, "If true, QUIC will default enable MTU discovery at server, with a target of 1450 bytes.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_enable_server_on_wire_ping, true, true, "If true, enable server retransmittable on wire PING.")
diff --git a/quiche/quic/core/crypto/crypto_protocol.h b/quiche/quic/core/crypto/crypto_protocol.h
index 47a5d8f..e29b4a2 100644
--- a/quiche/quic/core/crypto/crypto_protocol.h
+++ b/quiche/quic/core/crypto/crypto_protocol.h
@@ -378,6 +378,7 @@
                                // timeout.
 
 DEFINE_STATIC_QUIC_TAG(3AFF);  // 3 anti amplification factor.
+DEFINE_STATIC_QUIC_TAG(5AFF);  // 5 anti amplification factor.
 DEFINE_STATIC_QUIC_TAG(10AF);  // 10 anti amplification factor.
 
 // Enable path MTU discovery experiment.
diff --git a/quiche/quic/core/quic_connection.cc b/quiche/quic/core/quic_connection.cc
index 57b9181..1ff58d4 100644
--- a/quiche/quic/core/quic_connection.cc
+++ b/quiche/quic/core/quic_connection.cc
@@ -526,6 +526,11 @@
   if (config.HasClientRequestedIndependentOption(k3AFF, perspective_)) {
     anti_amplification_factor_ = 3;
   }
+  if (GetQuicReloadableFlag(quic_enable_5aff_connection_option) &&
+      config.HasClientRequestedIndependentOption(k5AFF, perspective_)) {
+    QUIC_RELOADABLE_FLAG_COUNT(quic_enable_5aff_connection_option);
+    anti_amplification_factor_ = 5;
+  }
   if (config.HasClientRequestedIndependentOption(k10AF, perspective_)) {
     anti_amplification_factor_ = 10;
   }