Getting error: You need to pass a model name to the store's modelFor method

Using Ember 2.6.0

Have the following routes defined:

Router.map(function() {
  this.route('brands');
  this.route('brand', {path: '/brands/:brand_id'});
});

The model for brand is:

export default Model.extend({
  name: attr('string'),
  description: attr('string'),
  dateCreated: attr('date'),
  lastUpdated: attr('date'),
  regions: hasMany('region')
});

And the model for region is:

export default Model.extend({
  name: attr('string'),
  dateCreated: attr('date'),
  lastUpdated: attr('date'),
  brand: belongsTo('brand')
});

Now, when trying to access /brands I am doing this in the route:

export default Ember.Route.extend({
  model() {
    return this.store.findAll('brand');
  }
});

I am getting the following error:

You need to pass a model name to the store's modelFor method

This worked prior to adding the brand route and region relationships. Brand is the parent, so I'm not sure why this isn't working.