Mongoose nested object unexpectd value

mongoose-schema.js

var mongoose = require("mongoose");

var schema = new mongoose.Schema({
  nestedProp: {
    bar: String,
    baz: String,
  },
});

var MyModel = mongoose.model("MyModel", schema);

var foo = new MyModel();
foo.set("nestedProp", {});
console.log(foo.get("nestedProp"));
// -> `null`, expected `{}`

This might be related to you.
Automattic/mongoose#1148