MTOM problem

I am trying to access a WSDL file directly in my Ruby. I have no
problems accessing the WSDL and sending a request to the web service
linked to the WSDL, but I am having a problem sending an MTOM attachment
to the service. In my Ruby code, I specify a parameter with an object
of type File:

“Attachment” =>

However, when I look at the SOAP message created, the AttachedObject
parameter is empty. Does anyone know if Ruby (specifically, SOAP4R) has
full MTOM support? Thanks!