distutils/command/dist.py contains this code # -- Metadata query methods ---------------------------------------- ... def get_version(self): return self.version or "???" which returns '???' as a version number if none is specified in the setup script. Since the bdist commands construct a filename containing the version number this leads to an invalid filename under windows, and the builds fail with a traceback like this: zip -rq D:\workspace\projects\epos\bin\dist\startup-???.win32.zip . creating 'D:\workspace\projects\epos\bin\dist\startup-???.win32.zip' and adding '.' to it error: D:\workspace\projects\epos\bin\dist\startup-???.win32.zip: Invalid argument The fix for bug #409403 (Signal an error if the distribution's metadata has no version) fixed this behaviour by requiring a version number: if self.metadata.version is None: raise DistutilsSetupError, \ "No version number specified for distribution" In the meantime, version 1.47 of dist.py, this code has been removed again. Log message: "Back out the requirement to supply a version number". Why was this done? I do not know whether we should require a version number or not, but at least the "???" string literal should be changed to something which can be part of a valid filename under windows (although IMO 'UNKNOWN' isn't really a better version number than '???')... Thomas