NullReferenceException with Set/Push Response

Greeting everyone, When I'm trying to Set or Push to Firebase, I'm getting following error System.NullReferenceException was unhandled by user code

 public class Todo
{
  public string name;
  public int priority;
}

var todo = new Todo
{
   name = "Execute SET",
   priority = 2
};
SetResponse response = await _client.SetAsync("todos/set", todo);
Todo result = response.ResultAs<Todo>(); //The response will contain the data written

I'm getting the error in SetResponse response = await _client.SetAsync("todos/set", todo); line.

Just to mention, I can read from firebase, but I cannot update/set in firebase.

bugthesystem / FireSharp

NullReferenceException with Set/Push Response #81