diff --git a/test/resources/firefox/user.js b/test/resources/firefox/user.js
index d4b9d4130..7ca293923 100644
--- a/test/resources/firefox/user.js
+++ b/test/resources/firefox/user.js
@@ -32,3 +32,4 @@ user_pref("app.update.enabled", false);
 user_pref("browser.panorama.experienced_first_run", true); // Assume experienced
 user_pref("dom.w3c_touch_events.enabled", true);
 user_pref("extensions.checkCompatibility", false);
+user_pref("extensions.installDistroAddons", false); // prevent testpilot etc