Stop ember from concatenating model name to adapter's namespace

I have an API that expects a GET request at this URI:

/rooms/500

which will return all of the conference rooms that hold 500 people. The number could differ as it is entered by the user.

I am using Ember.js and my adapter looks like this, hardcoded for testing:

import DS from 'ember-data';

export default DS.RESTAdapter.extend({
   namespace: 'rooms/500',
});

But the model name (rooms) always gets concatenated to the request, making it /rooms/500/rooms, for which there is no endpoint. How can I get Ember to stop changing the namespace?

Thank you.