It think happens with setuptools < 60.0.8 and python 3.9 actually. Regardless of it being ubuntu or macOS. I think you are lacking a language="c++" in the Extension in setup.py. I will check in a bit. -- Reply to this email directly or view it on GitHub: https://github.com/xrootd/xrootd/issues/1660#issuecomment-1074879307 You are receiving this because you are subscribed to this thread. Message ID: <[log in to unmask]> ######################################################################## Use REPLY-ALL to reply to list To unsubscribe from the XROOTD-DEV list, click the following link: https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=XROOTD-DEV&A=1