Iron Router "not found" template flashing up

Hey guys,

I am using IronRouter and a route that renders one specific article.
The articlie is retrieved from the database via a unique string (a slug) which is part of the url.

I want to render a notFound template if the slug in the url is wrong (eg. does not exist).


  this.route('article', {
    path: '/artikel/:slug',
    template: 'article',
    waitOn: function() {
      return Meteor.subscribe('one-article', this.params.slug);
    data: function() {
      return Articles.findOne({slug: this.params.slug});
    onAfterAction: function() {
      if (!Meteor.isClient) {
      var article = Articles.findOne({slug: this.params.slug});
      if (!article) {

The problem with this code is that even if the slug is valid, the not found template flashes up for a few seconds before the article is rendered.

Has anyone had this problem before?
How did you solve it?