META() does not serialize correctly

A call like this using the META() function:

  var query = context.Query<Beer>().Select(p => N1Ql.Meta(p)).Take(1)

returns the following JSON:

{"cas":0.0,"flags":0,"id":null,"type":null}

Note that the correct JSON document is being sent across the wire, so it must be something on the SDK or Linq side.