diff --git a/ghost/admin/mirage/serializers/application.js b/ghost/admin/mirage/serializers/application.js
index 8de724e520..05f2af0352 100644
--- a/ghost/admin/mirage/serializers/application.js
+++ b/ghost/admin/mirage/serializers/application.js
@@ -19,6 +19,10 @@ export default RestSerializer.extend({
         return underscore(relationship);
     },
 
+    keyForForeignKey(relationshipName) {
+        return `${underscore(relationshipName)}_id`;
+    },
+
     serialize(object, request) {
         // Ember expects pluralized responses for the post, user, and invite models,
         // and this shortcut will ensure that those models are pluralized