diff --git a/test/test.mjs b/test/test.mjs
index b46b789bd..a5cc117be 100644
--- a/test/test.mjs
+++ b/test/test.mjs
@@ -916,6 +916,8 @@ async function startBrowser({
     options.protocol = "webDriverBiDi";
 
     options.extraPrefsFirefox = {
+      // Disable system addon updates.
+      "extensions.systemAddon.update.enabled": false,
       // avoid to have a prompt when leaving a page with a form
       "dom.disable_beforeunload": true,
       // Disable dialog when saving a pdf