bootstrap on windows fails because ~\.cache\cerbero-sources doesn't exist

Trying to bootstrap on a clean(ish) windows install:

$ ./cerbero-uninstalled -c config/win32.cbc bootstrap
WARNING: Using default configuration because C:/MinGW/msys/1.0/home/Tim/.cerbero/cerbero.cbc is missing
Traceback (most recent call last):
  File "./cerbero-uninstalled", line 9, in <module>
    main()
  File ".\cerbero\main.py", line 135, in main
    Main(sys.argv[1:])
  File ".\cerbero\main.py", line 55, in __init__
    self.load_config()
  File ".\cerbero\main.py", line 103, in load_config
    self.config.load(self.args.config)
  File ".\cerbero\config.py", line 161, in load
    self._load_last_defaults()
  File ".\cerbero\config.py", line 518, in _load_last_defaults
    self.set_property('local_sources', self._default_local_sources_dir())
  File ".\cerbero\config.py", line 570, in _default_local_sources_dir
    return (cache_dir / 'cerbero-sources').resolve().as_posix()
  File "c:\Python35\lib\pathlib.py", line 1094, in resolve
    s = self._flavour.resolve(self)
  File "c:\Python35\lib\pathlib.py", line 186, in resolve
    return self._ext_to_normal(_getfinalpathname(s))
FileNotFoundError: [WinError 3] The system cannot find the path specified: 'C:\\Users\\Tim\\.cache\\cerbero-sources'