diff --git a/addons/web/static/tests/helpers/mock_server.js b/addons/web/static/tests/helpers/mock_server.js
index 891201b7d79..6839223a903 100644
--- a/addons/web/static/tests/helpers/mock_server.js
+++ b/addons/web/static/tests/helpers/mock_server.js
@@ -335,7 +335,7 @@ var MockServer = Class.extend({
                 activeInDomain = activeInDomain || subdomain[0] === 'active';
             });
             if (!activeInDomain) {
-                domain.unshift(['active', '=', true]);
+                domain = [['active', '=', true]].concat(domain);
             }
         }