diff --git a/src/legacy/ui/public/new_platform/new_platform.karma_mock.js b/src/legacy/ui/public/new_platform/new_platform.karma_mock.js
index 990811442e3e..10d2818df279 100644
--- a/src/legacy/ui/public/new_platform/new_platform.karma_mock.js
+++ b/src/legacy/ui/public/new_platform/new_platform.karma_mock.js
@@ -68,6 +68,7 @@ export const mockUiSettings = {
   getUpdate$: () => ({
     subscribe: sinon.fake(),
   }),
+  isDefault: sinon.fake(),
   'query:allowLeadingWildcards': true,
   'query:queryString:options': {},
   'courier:ignoreFilterIfFieldNotInIndex': true,