--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -1561,17 +1561,18 @@ pref("browser.tabs.remote.desktopbehavio
 // We leave it here set to false to reset users' defaults and allow
 // us to change everybody to true in the future, when desired.
 pref("browser.tabs.remote.autostart.1", false);
 pref("browser.tabs.remote.autostart.2", true);
 #endif
 
 // For speculatively warming up tabs to improve perceived
 // performance while using the async tab switcher.
-pref("browser.tabs.remote.warmup.enabled", true);
+// Disabled until bug 1397426 is fixed.
+pref("browser.tabs.remote.warmup.enabled", false);
 pref("browser.tabs.remote.warmup.maxTabs", 3);
 pref("browser.tabs.remote.warmup.unloadDelayMs", 2000);
 
 // For the about:tabcrashed page
 pref("browser.tabs.crashReporting.sendReport", true);
 pref("browser.tabs.crashReporting.includeURL", false);
 pref("browser.tabs.crashReporting.requestEmail", false);
 pref("browser.tabs.crashReporting.emailMe", false);