diff --git a/js/tests/e4x/Regress/regress-308111.js b/js/tests/e4x/Regress/regress-308111.js
index 08b305d1579..036dfd1b430 100644
--- a/js/tests/e4x/Regress/regress-308111.js
+++ b/js/tests/e4x/Regress/regress-308111.js
@@ -308,7 +308,6 @@ var xml = <prefs>
 <pref><name>dom.popup_maximum</name></pref>
 <pref><name>security.warn_entering_secure</name></pref>
 <pref><name>mousewheel.horizscroll.withaltkey.numlines</name></pref>
-<pref><name>javascript.allow.mailnews</name></pref>
 <pref><name>browser.tabs.warnOnCloseOther</name></pref>
 <pref><name>intl.accept_charsets</name></pref>
 <pref><name>font.name.monospace.x-central-euro</name></pref>
diff --git a/modules/libpref/src/init/all.js b/modules/libpref/src/init/all.js
index 2699497c1d7..6a84f3b0d76 100644
--- a/modules/libpref/src/init/all.js
+++ b/modules/libpref/src/init/all.js
@@ -537,7 +537,6 @@ pref("privacy.popups.disable_from_plugins", 2);
 pref("dom.event.contextmenu.enabled",       true);
 
 pref("javascript.enabled",                  true);
-pref("javascript.allow.mailnews",           false);
 pref("javascript.options.strict",           false);
 pref("javascript.options.relimit",          false);
 pref("javascript.options.jit.content",      true);
diff --git a/testing/sisyphus/prefs/mail-user.js b/testing/sisyphus/prefs/mail-user.js
index 92dc0e2d754..0faafc36602 100644
--- a/testing/sisyphus/prefs/mail-user.js
+++ b/testing/sisyphus/prefs/mail-user.js
@@ -12,7 +12,6 @@ user_pref("dom.allow_scripts_to_close_windows", true);
 user_pref("dom.max_script_run_time", 0);
 user_pref("extensions.update.enabled", false);
 user_pref("extensions.update.notifyUser", false);
-user_pref("javascript.allow.mailnews", true);
 user_pref("mail.startup.enabledMailCheckOnce", false);
 user_pref("security.enable_java", false);
 user_pref("security.warn_submit_insecure", false);
diff --git a/testing/sisyphus/prefs/public-user.js b/testing/sisyphus/prefs/public-user.js
index e28e2dfe8dd..a87d7ef2cdc 100644
--- a/testing/sisyphus/prefs/public-user.js
+++ b/testing/sisyphus/prefs/public-user.js
@@ -16,7 +16,6 @@ user_pref("dom.disable_window_flip", true);
 user_pref("dom.disable_window_open_feature.status", true);
 user_pref("dom.max_script_run_time", 0);
 user_pref("dom.max_chrome_script_run_time", 0);
-user_pref("javascript.allow.mailnews", false);
 user_pref("javascript.options.showInConsole", true);
 user_pref("layout.css.report_errors", true);
 user_pref("security.enable_java", false);
diff --git a/testing/sisyphus/prefs/test-user.js b/testing/sisyphus/prefs/test-user.js
index 5d683ca9c9b..d1061dbed85 100644
--- a/testing/sisyphus/prefs/test-user.js
+++ b/testing/sisyphus/prefs/test-user.js
@@ -13,7 +13,6 @@ user_pref("dom.allow_scripts_to_close_windows", true);
 user_pref("dom.disable_open_during_load", false);
 user_pref("dom.max_script_run_time", 0);
 user_pref("dom.max_chrome_script_run_time", 0);
-user_pref("javascript.allow.mailnews", true);
 user_pref("javascript.options.showInConsole", true);
 user_pref("layout.css.report_errors", true);
 user_pref("security.enable_java", false);