Relationship must be key/value pair

Getting the following error:

firebase.js:119 Uncaught Error: thunder@model:provider: relationship hasMany('address') must be a key/value map. Example: { "address": { "address_1": true } } instead got: "-KDehK2aAE15KEQXjHC-"

Address Model

export default DS.Model.extend({
  city: DS.attr('string'),
  state: DS.attr('string'),
  street: DS.attr('string'),
  zip: DS.attr('string'),
  provider: DS.belongsTo('provider')
});

Provider Model

export default DS.Model.extend({
  category: DS.attr('string'),
  status: DS.attr('boolean'),
  name: DS.attr('string'),
  description: DS.attr('string'),
  address: DS.hasMany('address', {async: true}),
  phone: DS.attr('string'),
  email: DS.attr()
});

Here is what I have in Firebase