The ./configure script prints a warning when passed this flag, starting with 3.7: configure: WARNING: unrecognized options: --with-threads The reason is that there's no longer such a thing as a build without threads. Eliminate the warning, by only passing the flag on the older releases that accept it. Upstream change and discussion: https://github.com/python/cpython/commit/a6a4dc816 https://bugs.python.org/issue31370