[Zope] Uploading rst docs & Put_factory

I want to upload a restructured text (rst) document to my Zope server via FTP and have its content type recognized. I understand that I need to make an entry in PUT_factory.py but I need some guidance here. The following attempt didn't have any effect (that is, the type of the uploaded file is still just 'text/plain'): elif typ.endswith('rst'): ob= ReStructuredTextDocument(name)