Receiving an attachment via MTOM by consuming webservice

On consuming a webservice, I get a response in SoapUI like shown below: an XOP attachment with the requested file (MTOM, base64-encoded). In Mendix however, the stream results into an empty String or an empty FileDocument (Binary) when the response is mapped using the XML import mapping.

Should Mendix be able to handle these webservice responses with attachments? Or is there an alternative to receive these responses?