When building an SDist via pipx run build, flit doesn't include LICENSE* files, so when building the wheel also via pipx run build, there are no licenses files unless there is a license = {files = ...} key (and then only one file is allowed). However, when directly building the wheel, using pipx run build --wheel without going through an SDist first, then LICENSE* is included, see

#540 is slightly related. Noticed when trying to setup packaging on Flit in pypa/packaging#340 (comment) .