how to store boolean value in mongodb using express js

i’m trying to store a boolean in mongodb but it always returns false
here’s my database

const UserSchema = new Schema({
  name: String,
  password: {
    type: String,
    required: true
  },
  isAdmin: {
    type: Boolean,
    default: false
},

this how i post the request using postman

{ 
    "name": "aj",
    "password":"aj",
    "admin": true
}

this the result i get in my database

isAdmin:false
name:"aj"
password:"$2a$10$wBfElJ3YbZoOk3Bz/tyFc.uzZGuzStDppDCINZ8mZexZKumnDMmoW"

please how can i set it admin to true or false when registering