diff --git a/src/group/dto/create-group.dto.ts b/src/group/dto/create-group.dto.ts
index 5da499e..0b11ec2 100644
--- a/src/group/dto/create-group.dto.ts
+++ b/src/group/dto/create-group.dto.ts
@@ -1,5 +1,4 @@
 import { ApiProperty } from '@nestjs/swagger';
-import { ObjectId } from 'mongoose';
 
 export class CreateGroupDto {
   @ApiProperty({
@@ -31,7 +30,7 @@ export class CreateGroupDto {
   })
   readonly subManagers: [
     {
-      user: ObjectId;
+      user: string;
       authorities: string[];
     },
   ];
diff --git a/src/group/schemas/group.schema.ts b/src/group/schemas/group.schema.ts
index 4845f2c..f35f831 100644
--- a/src/group/schemas/group.schema.ts
+++ b/src/group/schemas/group.schema.ts
@@ -3,10 +3,7 @@ import * as mongoose from 'mongoose';
 export const GroupSchema = new mongoose.Schema({
   name: String,
   description: String,
-  manager: {
-    type: mongoose.Schema.Types.ObjectId,
-    ref: 'User',
-  },
+  manager: String,
   subManagers: [
     {
       user: String,