diff --git a/quic/core/quic_flags_list.h b/quic/core/quic_flags_list.h
index 0a529ae..6591a87 100644
--- a/quic/core/quic_flags_list.h
+++ b/quic/core/quic_flags_list.h
@@ -126,7 +126,7 @@
 // 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.
-QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_blocked_ports, false)
+QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_blocked_ports, true)
 // When true, defaults to BBR congestion control instead of Cubic.
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_default_to_bbr, false)
 // When true, prevents QUIC\'s PacingSender from generating bursts when the congestion controller is CWND limited and not pacing limited.