--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -4800,17 +4800,17 @@ pref("network.tcp.keepalive.idle_time", 
 pref("network.tcp.keepalive.retry_interval", 1); // seconds
 #endif
 // Default maximum probe retransmissions.
 // Linux only; not configurable on Win and Mac; fixed at 10 and 8 respectively.
 #if defined(XP_UNIX) && !defined(XP_MACOSX)
 pref("network.tcp.keepalive.probe_count", 4);
 #endif
 
-pref("network.tcp.tcp_fastopen_enable", true);
+pref("network.tcp.tcp_fastopen_enable", false);
 pref("network.tcp.tcp_fastopen_consecutive_failure_limit", 5);
 
 // Whether to disable acceleration for all widgets.
 pref("layers.acceleration.disabled", false);
 // Preference that when switched at runtime will run a series of benchmarks
 // and output the result to stderr.
 pref("layers.bench.enabled", false);