diff --git a/x-pack/test/cases_api_integration/security_and_spaces/tests/common/cases/find_cases.ts b/x-pack/test/cases_api_integration/security_and_spaces/tests/common/cases/find_cases.ts
index 65f3a36cbe487..3daa29c02b107 100644
--- a/x-pack/test/cases_api_integration/security_and_spaces/tests/common/cases/find_cases.ts
+++ b/x-pack/test/cases_api_integration/security_and_spaces/tests/common/cases/find_cases.ts
@@ -238,9 +238,11 @@ export default ({ getService }: FtrProviderContext): void => {
 
       it('returns the correct fields', async () => {
         const postedCase = await createCase(supertest, postCaseReq);
+        // all fields that contain the UserRT definition must be included here (aka created_by, closed_by, and updated_by)
+        // see https://github.com/elastic/kibana/issues/139503
         const queryFields: Array<keyof CaseResponse | Array<keyof CaseResponse>> = [
-          'title',
-          ['title', 'description'],
+          ['title', 'created_by', 'closed_by', 'updated_by'],
+          ['title', 'description', 'created_by', 'closed_by', 'updated_by'],
         ];
 
         for (const fields of queryFields) {