XML File Upload Disallowed?

[AJHendrick]

I tried to upload a simple .xml file (about 380 KB) as a mod for Galactic Civilizations 3. However, the upload system barfed on step 8, saying it wasn't a proper file type? Can anyone point me to what I might have done wrong? Do I have to zip ir up, or otherwise obscure the .xml type for Nexus to accept it?

[RS13]

Yes, only archives can be uploaded.