FFYOO suggests: The key thing in the command I mentioned is that it builds an sdist, unpacks it, and builds a wheel from that source I would recommend you to do the same building directly from source jumps over https://setuptools.pypa.io/en/latest/userguide/miscellaneous.html setuptools, and some other backends, are not designed to work like that, they are designed to build the wheel from the sdist setuptools is usually the most problematic one, in the others issues mostly come from dirty development trees, etc https://github.com/pypa/build/blob/f219276a6e2c6c8222780ba518ce52444a91deaa/src/build/__main__.py#L260 Stefano