The latest release at https://libvirt.org/sources/libvirt-6.6.0.tar.xz includes a configure script that breaks Homebrew (and other builds on MacOS/Darwin). The breaking change is related to a new version of the file m4/libtool.m4; line 2648 was changed to: shrext_cmds='`test .$module = .yes && echo .bundle || echo .dylib`' However, src/driver.c loads modules with ".so" extensions, at line 56: if (!(modfile = virFileFindResourceFull(name, "libvirt_driver_", ".so", The released tarball for 6.5.0 had the same shrext_cmds as upstream libtool: shrext_cmds='`test .$module = .yes && echo .so || echo .dylib`' Not sure where to submit the issue (as the m4 files aren't in libvirt source control)... it appears to only affect the distribution tarball. Perhaps the tarball could be re-released with autoconf from the official upstream libtool? (2.4.6) Thanks, Scott PS. MacPorts is unaffected as it runs autogen.sh... but that shouldn't be necessary with a distribution tarball :)