diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index c1c50c25af..ecf29bef53 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -2752,8 +2752,11 @@ pref("editor.resizing.preserve_ratio",       true);
 pref("editor.positioning.offset",            0);
 
 pref("dom.use_watchdog", true);
-pref("dom.max_chrome_script_run_time", 90);
-pref("dom.max_script_run_time", 20);
+pref("dom.max_chrome_script_run_time", 30);
+pref("dom.max_script_run_time", 15);
+
+// Automatically terminate non-responsive scripts if script_run_time expires.
+pref("dom.always_stop_slow_scripts", false);
 
 // Stop all scripts in a compartment when the "stop script" dialog is used.
 pref("dom.global_stop_script", true);