MapBox-GL Source / addSource bug

I'm getting this error **Uncaught TypeError: Cannot read property 'sources' of undefined** (mapbox-gl.js:4) when trying to load a tile as a mapbox-gl source.

<div id='map' style='height:500px;width:700px;'>    
</div>

<script>
    var accessToken='<my access token>'
    mapboxgl.accessToken = accessToken;
    var map = new mapboxgl.Map({
      container: 'map',
      style: 'https://www.mapbox.com/mapbox-gl-styles/styles/outdoors-v4.json', //stylesheet location
      center: [-34.6, -58.4],
      zoom: 11
    });
    var sourceObj = new mapboxgl.Source({
      type: 'vector',
      url: 'mapbox://<some map id>'
    });
    map.addSource('test',sourceObj);
</script>

If I don't load any source, everything works well. This happens with the 0.2.1 and 0.2.2 versions of the API. I tried with different tiles and I get the same problem.

Any clue?

Thanks in advance