emberJS mixin super override

How can i override a mixin but still keep the old mixin functionality.

I have a mixin that uses beforeModel, and have a route:

App.PlayRoute = Ember.Route.extend("beforeModelMixin", {
    beforeModel: {
        // Here i want to have mixin beforeModel functionality as well as my own hook.
    }
}

Above example beforeModelMixin gets overriden and doesn't work anymore, because i defined beforeModel again.

Is that possible?