Mongoose Latitude & Longitude validation is not working while saving in mongo?

Following is my schema for Location collection:

var LocationSchema = new Schema({
    street : {type: String, required: true},
    area : {type: String, required: true},
    city : {type: String, required: true},
    state : {type: String, required: true},
    zip : {type: String, required: true},
    country : {type: String, default: 'IN'},
    pointers:{type: [], index: '2dsphere'}
});

While saving data in mongo using mongoose pointers are store as string not as number. Got following response:

"street": "rani sati marg",
"area": "malad east",
"city": "mumbai",
"state": "maharashtra",
"zip": "400097",
"pointers": [
    "72.857452,19.857452"
],
"country": "IN"

I want pointer values in number like: [72.857452,19.857452]