Ember data error: model:@each`, must be of the form `type:name

I have this model, that throws an error when I navigate to this route with this model:

export default DS.Model.extend({
  newUser: DS.belongsTo('user'),
  password: DS.attr('string')
});

user model:

export default DS.Model.extend({
  title: DS.attr('string'),
  firstName: DS.attr('string'),
  surname: DS.attr('string'),
  dateOfBirth: DS.attr('string'),
  telephoneNumber: DS.attr('string'),
  accountType: DS.belongsTo('accountType'),
  emailAddress: DS.attr('string'),

  //used to present full-name
  fullName: function () {
    return this.get('title') + ' ' +
      this.get('firstName') + ' ' +
      this.get('surname');
  }.property("title", "firstName", "surname")

});

error:

model:@each`, must be of the form `type:name