Hi, Robert Vollmert skribis: > rob@garp ~/guix$ nano gnu/packages/haskell.scm > rob@garp ~/guix$ ./pre-inst-env guix build ghc-ansi-wl-pprint I’d suggest running “make” once you’ve edited a file. It’s not strictly necessary (Guile then simply evaluates code instead of running compiled code), but it will allow you to get rid of these warnings, the compiler might warn you ahead of time of possible mistakes, and the whole thing will be slightly faster. Does that make sense? Ludo’.