diff --git a/quic/core/quic_flags_list.h b/quic/core/quic_flags_list.h
index 1fc2236..cb4e655 100644
--- a/quic/core/quic_flags_list.h
+++ b/quic/core/quic_flags_list.h
@@ -59,7 +59,7 @@
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_testonly_default_false, false)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_testonly_default_true, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_tls_use_normalized_sni_for_cert_selectioon, false)
-QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_tls_use_per_handshaker_proof_source, false)
+QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_tls_use_per_handshaker_proof_source, true)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_unified_iw_options, false)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_unify_stop_sending, false)
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_update_packet_content_returns_connected, true)