diff --git a/test/features/assignment.test.js b/test/features/assignment.test.js
index 990f3ff..1df0e26 100644
--- a/test/features/assignment.test.js
+++ b/test/features/assignment.test.js
@@ -73,7 +73,7 @@ describe("Assignment Comfirm Page Feature", function () {
         url: "moz-extension://fake/confirm-page.html?" +
                `url=${encodeURIComponent(url)}` +
                `&cookieStoreId=${this.webExt.tab.cookieStoreId}`,
-        cookieStoreId: undefined,
+        cookieStoreId: "firefox-default",
         openerTabId: null,
         index: 2,
         active: true