mongoose - Sort does not work on population query -

my code shown below:

var orderhistory = function(req, res) {     order.find({             'customer_id': req.body.user_id.trim()         }).populate('foodtruck_id','-item_list').populate('items').populate('customer_id').sort({order_time: -1})         .exec(function(err, orders) {             if (err) res.json({                 status: '404',                 message: 'sorry, there no data'             });             res.json({                 status: '200',                 message: 'order list',                 data: orders             });         }); }; 

order.js

var mongoose = require('mongoose'); var schema = mongoose.schema; var foodtruck = require('./foodtruck.js'); var payment = require('./payment.js'); var items = require('./items.js');   var order = new schema({     order_status:number,   //0 place 1 accepted 2 cooked 3 cancelled     foodtruck_id:{type:schema.types.objectid,ref: 'foodtruck'},     customer_id:{type: schema.types.objectid,ref: 'user'},     items:[{type : schema.types.objectid, ref : 'items'}],     user_type:boolean,     order_time:date,     order_rating:{type:number,default:5.0},     order_issue_comments:string,     order_special_instruction:string,     order_total:number,     order_location:string,     order_coupon_code:string,     payment_id:{type:schema.types.objectid,ref:'payment'} },{ versionkey: false });   module.exports = mongoose.model('order',order); 

now want is, want query result in descending order of order_time criteria, somehow not work. how can achieve requirement?