diff --git a/quiche/common/quiche_feature_flags_list.h b/quiche/common/quiche_feature_flags_list.h
index 1d45e52..23c44df 100755
--- a/quiche/common/quiche_feature_flags_list.h
+++ b/quiche/common/quiche_feature_flags_list.h
@@ -30,7 +30,7 @@
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_disable_version_q046, false, true, "If true, disable QUIC version Q046.")
 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_ecn_in_first_ack, false, false, "When true, reports ECN in counts in the ACK of the a client initial that goes in the buffered packet store.")
+QUICHE_FLAG(bool, quiche_reloadable_flag_quic_ecn_in_first_ack, false, true, "When true, reports ECN in counts in the ACK of the a client initial that goes in the buffered packet store.")
 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_new_chaos_protector, false, false, "If true, use new refactored QuicChaosProtector implementation.")