The following message was received to the mailing list and, for some reason, discarded instead of held for moderation (if you want to submit emails to asdf-devel, please subscribe; you can always unsubscribe later.) This certainly seems plausibly to be a bug. Please post it at [GitLab](https://gitlab.common-lisp.net/asdf/asdf/-/issues) and I will have a look at it as time permits. A test case would be a real plus -- I'm much more likely to get on this if I don't also have to create the test case myself. ---- Hello, I may have discovered a bug in ASDF. In the function COMPUTE-ACTION-STAMP, first the IN-STAMPS and then the OUT-STAMPS are collected. When one of the last write dates are not available, T is returned by GET-FILE-STAMP, which is deemed infinitely old by TIMESTAMP<=. But suppose that all the IN-STAMPS and at least one of the OUT-STAMPS are not available, then LATEST-IN and EARLIEST-OUT are both T, and the wisest thing would probably be rebuild everything, but TIMESTAMP<= returns T so nothing is built. What do you think? Andrea Monaco