toJSON doesn't serialize attached models

[toddself]

Example:

var Backbone = require('backbone');
var mongoSync = require('backbone-mongo').sync;

var Inner = Backbone.Model.extend({
    urlRoot: 'mongodb://localhost:27017/inner'
});
Inner.prototype.sync = mongoSync(Inner);

var Outer = Backbone.Model.extend({
    urlRoot: 'mongodb://localhost:27017/outer',
   schema: {
        inner: function(){
            return ['hasOne', Inner];
        }
    }
});
Outer.prototype.sync = mongoSync(Outer);

var outer = new Outer();
outer.set({foo: 'bar', inner: new Inner({fie: 'baz'})});
{ cid: 'c5',
  attributes:
   { howdy: 'ho',
     inner:
      { cid: 'c10',
        attributes: [Object],
        _changing: false,
        _previousAttributes: {},
        changed: {},
        _pending: false,
        _orm: [Object] } },
  changed:
   { inner:
      { cid: 'c10',
        attributes: [Object],
        _changing: false,
        _previousAttributes: {},
        changed: {},
        _pending: false,
        _orm: [Object] } },
  _orm:
   { needs_load: {},
     is_initialized: true,
     rel_dirty: { inner: true } },
  _changing: false,
  _previousAttributes: { howdy: 'ho' },
  _pending: false }

outer.get('inner');
{ cid: 'c10',
  attributes: { fie: 'baz' },
  _changing: false,
  _previousAttributes: {},
  changed: {},
  _pending: false,
  _orm: { needs_load: {}, is_initialized: true } }

outer.toJSON();
{foo: 'bar'}

Expected:

outer.toJSON();
{
    foo: 'bar',
    inner: {
        fie: 'baz'
    }
}

[toddself]

Wait. There's no way this could work. oops!