[Zope] Storing files or fileobjects in Session

I want to store files (from HTTP FileToUpload) or file objects in a Session object. It's for a wizard thing. No sessioning products can store files or object as far as I know, but they can save references to them and that way simulate it as if you're storing objects in the session. Is there anything prepared like this that will save me time? If not, I'll write something that saves files as objects and stores the id in a session and then I'll sniff the id again to see if it can return the real object. Peter