Hi all, We've been able to hold out for a long time, but this is to let you all know that we have now had to switch the numpy build to rely on setuptools: https://github.com/numpy/numpy/pull/6895. Main reason: plain distutils doesn't support PEP 440 naming. See https://github.com/numpy/numpy/issues/6257 and https://github.com/numpy/numpy/issues/6551 for details. So if you see different build weirdness on master, it's likely due to this change. Cheers, Ralf