ASP.NET MVC3 JSON Model-binding with nested class

In MVC3, is it possible to automatically bind javascript objects to models if the model has nested objects? My model looks like this:

 public class Tweet
 {
    public Tweet()
    {
         Coordinates = new Geo();
    }
    public string Id { get; set; }
    public string User { get; set; }
    public DateTime Created { get; set; }
    public string Text { get; set; }
    public Geo Coordinates { get; set; } 

}

public class Geo {

    public Geo(){}

    public Geo(double? lat, double? lng)
    {
        this.Latitude = lat;
        this.Longitude = lng;
    }

    public double? Latitude { get; set; }
    public double? Longitude { get; set; }

    public bool HasValue
    {
        get
        {
            return (Latitude != null || Longitude != null);
        }
    }
}

When I post the following JSON to my controller everything except "Coordinates" binds successfully:

{"Text":"test","Id":"testid","User":"testuser","Created":"","Coordinates":{"Latitude":57.69679752892457,"Longitude":11.982091465576104}}

This is what my controller action looks like:

    [HttpPost]
    public JsonResult ReTweet(Tweet tweet)
    {
        //do some stuff
    }

Am I missing something here or does the new auto-binding feature only support primitive objects?