Glad you got it working.  In general, it is probably a good idea to do a "make clean" before or after re-running ./configure in a particular build directory.   Ideally, the Makefile dependencies should detect and do the right thing automatically so that a manual "make clean" would not be necessary but, with as complicated a build system as we have, that goal might be unrealistic (PRs welcome though!). In any case adding something to the devguide steps would also be a good idea. Again, an issue and/or a PR against the devguide would be welcome (https://github.com/python/devguide).