Below is the code: var lookupReqBuilder = PermissionService.LookupSubjectsRequest.newBuilder() .setPermission(permissionName) .setResource(Core.ObjectReference.newBuilder() .setObjectType(prefixedResource(tenantPrefix, resource)) .setObjectId(resourceId) .build()); var lookupReq = lookupReqBuilder.build(); try{ Iterator respIterator = permissionsService.lookupSubjects(lookupReq); return StreamSupport.stream(Spliterators.spliteratorUnknownSize(respIterator, Spliterator.ORDERED), false) .map(PermissionService.LookupSubjectsResponse::getSubjectObjectId) .collect(Collectors.toSet()) .stream() .toList(); } catch (Exception e){ log.error("Error occured", e); throw e; } the lookupReq object has : permission_:"doc1_view"; "resource_ : objectType_: "local/client", objectId_: "keys"; subjectObjectType_: "" io.grpc.StatusRuntimeException: INVALID_ARGUMENT: invalid LookupSubjectsRequest.SubjectObjectType: value does not match regex pattern "^([a-z][a-z0-9_]{1,61}[a-z0-9]/)*[a-z][a-z0-9_]{1,62}[a-z0-9]$"