Hi, On Wed, 23 Feb 2022 at 12:27, Philip Munksgaard wrote: > The relevant section states: > > > This option outputs a directory if the package requires multiple registrations: this can occur if internal/convenience libraries are used. These configuration file names are sorted so that they can be registered in order. > > 0: https://downloads.haskell.org/cabal/Cabal-3.0.0.0/doc/users-guide/installing-packages.html#cmdoption-setup-register-gen-pkg-config Thanks. Indeed, it may be the issue. > I think we need to amend `haskell-build-system.scm` to be able to handle such cases. Well, such change is a core-updates change because it will rebuild the world. Let see if in the meantime, the attoparsec package could be patched. Cheers, simon