diff --git a/backend/src/services/model.ts b/backend/src/services/model.ts
index 967535423..7ea0ac3b3 100644
--- a/backend/src/services/model.ts
+++ b/backend/src/services/model.ts
@@ -12,9 +12,9 @@ import ModelCardRevisionModel, {
 } from '../models/ModelCardRevision.js'
 import { UserInterface } from '../models/User.js'
 import { GetModelCardVersionOptions, GetModelCardVersionOptionsKeys, GetModelFiltersKeys } from '../types/enums.js'
-import { EntryUserPermissions } from '../types/types.js'
+import { EntityKind, EntryUserPermissions } from '../types/types.js'
 import { isValidatorResultError } from '../types/ValidatorResultError.js'
-import { toEntity } from '../utils/entity.js'
+import { fromEntity, toEntity } from '../utils/entity.js'
 import { BadReq, Forbidden, InternalError, NotFound } from '../utils/error.js'
 import { convertStringToId } from '../utils/id.js'
 import { authResponseToUserPermission } from '../utils/permissions.js'
@@ -377,7 +377,8 @@ async function validateCollaborators(
         throw BadReq('Collaborator name must be a valid string')
       }
       // TODO we currently only check for users, we should consider how we want to handle groups
-      if (collaborator.startsWith('user:')) {
+      const { kind } = fromEntity(collaborator)
+      if (kind === EntityKind.USER) {
         await authentication.getUserInformation(collaborator)
       }
     }),
diff --git a/backend/src/types/types.ts b/backend/src/types/types.ts
index 8a8fe89f8..56b3a413e 100644
--- a/backend/src/types/types.ts
+++ b/backend/src/types/types.ts
@@ -3,6 +3,11 @@ export const RoleKind = {
   SCHEMA: 'schema',
 } as const
 
+export enum EntityKind {
+  USER = 'user',
+  GROUP = 'group',
+}
+
 export type RoleKindKeys = (typeof RoleKind)[keyof typeof RoleKind]
 
 export interface Role {