diff --git a/quiche/common/quiche_feature_flags_list.h b/quiche/common/quiche_feature_flags_list.h
index 92ed0cd..1320c02 100755
--- a/quiche/common/quiche_feature_flags_list.h
+++ b/quiche/common/quiche_feature_flags_list.h
@@ -40,7 +40,7 @@
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_enable_server_on_wire_ping, true, true, "If true, enable server retransmittable on wire PING.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_enable_version_rfcv2, false, false, "When true, support RFC9369.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_enobufs_blocked, true, true, "If true, ENOBUFS socket errors are reported as socket blocked instead of socket failure.")
-QUICHE_FLAG(bool, quiche_reloadable_flag_quic_fail_on_empty_ack, false, true, "If true, closes the connection if there are no packets in the ack frame. This is always the result of a protocol violation by the peer.")
+QUICHE_FLAG(bool, quiche_reloadable_flag_quic_fail_on_empty_ack, true, true, "If true, closes the connection if there are no packets in the ack frame. This is always the result of a protocol violation by the peer.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_fin_before_completed_http_headers, false, true, "If true, close the connection with error if FIN is received before finish receiving the whole HTTP headers.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_fix_timeouts, true, true, "If true, postpone setting handshake timeout to infinite to handshake complete.")
 QUICHE_FLAG(bool, quiche_reloadable_flag_quic_ignore_gquic_probing, true, true, "If true, QUIC server will not respond to gQUIC probing packet(PING + PADDING) but treat it as a regular packet.")