You are right. (I just tried myself). Although [Marshalling](http://spray.io/documentation/1.0-M8.1/spray-httpx/marshalling/) mentions content negotiation, it seems to be driven by the server instead of the client (see [Marshaller](https://github.com/spray/spray/blob/master/spray-httpx/src/main/scala/spray/httpx/marshalling/Marshaller.scala#L42-L45)).

@sirthias Is this intended behaviour?