Ember date belongTo with serialized id

App.Locale = DS.Model.extend
  language: DS.belongsTo("language")

App.LocaleSerializer = App.ApplicationSerializer.extend
   attrs:
     language:  { serialize: "id", deserialize: "records" }

Using ember with rails as the backend. I am trying to create a locale, which has a dropdown to select a language. My idea is to pass a language_id to the backend, however I get the following when I submit.

{"locale"=>{"language"=>"15" }

How do I convert this to look like

{"locale"=>{"language_id"=>"15" }

Thanks