Accessing parent route slug from route

I have a route /settings/:setting_id/overview. In my settings.js route I can see the value of setting_id in the model function, i.e.

export default Ember.Route.extend({
    model: function(params) {
        alert(params.setting_id);
    }
});

However, in my settings/overview.js route I get undefined for setting_id for the exact same code as above.

My router.js is defined as follows:

Router.map(function() {
    //...
    this.resource('settings', { path: 'settings/:settings_id' }, function() {
        this.route('overview');
        // ...
    });
 });