mongoose getters, not working.

gistfile1.js

var mongoose = require('mongoose'),
db = mongoose.connect('mongodb://localhost/blog'),
Schema = mongoose.Schema,
fields = ['createdDate', 'canComment', 'story', 'title', 'user'];

var commentsSchema = new Schema({
    user : { type: String },
    comment : { type: String },
    createdDate : { type: Date, default: Date.now }
});

var postsSchema = new Schema({
    user : { type: String },
    title : { type: String },
    story : { type: String },
    canComment: { type: Boolean },
    createdDate : { type: Date, get: function(dt) { return dt.valueOf(); }, default: Date.now },
    comments: [commentsSchema]
});

var Posts =  mongoose.model('posts', postsSchema);

Posts.find({}, fields).limit(10).execFind(function(err, res) {
	if (res != null) {
        console.log(res);
    }
});

I dont know if it is bug or a feature, but looks like getters work only when directly getting a property.

JSON.stringify(doc); //not working

doc.propertyWithGetter; //working