How do I include version information in the filemap.xml generated by Content Importer?

I'm trying to test importing translated content with Content Importer (we currently depend on the batch import system with disk directories). I've created a test directory for this purpose that is basically the extracted zip from an ordinary Content Manager translation export, and then tried to import that into our Tridion Docs instance. Conversion appears to succeed, but when I attempt to import each XML file fails with  "The version number must be supplied." The version number is indeed specified in the source XML, but for some reason the conversion process is stripping it out. How do I reconfigure conversion to enable translations to be imported with Content Importer?