Kirby 2.3.0 Beta

I played around with the plugin system and registered a blueprint as described here.
Everything works fine if I add the blueprint explicitly to other blueprints like this:

pages:
  template: 
    - my_plugin_blueprint
    - some
    - other
    - blueprints

But all pages with the following setting don’t recognize my plugin blueprint …

pages: true

Is this a bug? Any ideas?