--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -1492,17 +1492,17 @@ pref("network.http.fast-fallback-to-IPv4
 #ifdef RELEASE_BUILD
 pref("network.http.bypass-cachelock-threshold", 200000);
 #else
 pref("network.http.bypass-cachelock-threshold", 250);
 #endif
 
 // Try and use SPDY when using SSL
 pref("network.http.spdy.enabled", true);
-pref("network.http.spdy.enabled.v3-1", true);
+pref("network.http.spdy.enabled.v3-1", false);
 pref("network.http.spdy.enabled.http2", true);
 pref("network.http.spdy.enabled.deps", true);
 pref("network.http.spdy.enforce-tls-profile", true);
 pref("network.http.spdy.chunk-size", 16000);
 pref("network.http.spdy.timeout", 180);
 pref("network.http.spdy.coalesce-hostnames", true);
 pref("network.http.spdy.persistent-settings", false);
 pref("network.http.spdy.ping-threshold", 58);