The best way to sort a collection in a CompositeView

I am trying to sort a collection in a Marionette.CompositeView.
I have a collection which looks like this:

[
   {id: 1, name: 'bar'},
   {id: 2, name: 'boo' },
   {id: 3, name: 'foo' }
]

I need to sort the collection by id in reverse order.
Actually it work only when I reload the page.
When I add a new model, the new item is added apparently random to the list.
If I refresh the page, they will be well sorted.

My questions are:
1) how to fix the problem when I add a new model?
2) it will be possible to improve the code?

Here is my code:

return Marionette.CompositeView.extend({

    initialize: function () {
        this.collection.fetch();
    },

    onRender: function () {
        var collection =  this.collection;

        collection.comparator = function (collection) {
            return - collection.get('id');
        }
    },

    onSuccess: function () {
        this.collection.add(this.messageModel);
        this.collection.sort(); // the messageModel seems to be added 
                                // apparently randomly to the list. 
                                // only if I refresh the page it will be ok
    }
})