This combined with setting the `use-pkg-config` flag on `postgresql-libpq` should get it compiling. There is still a problem with `openssl` that requires a `module` to fix the linking of executables. Add the following to the `cabal.project` file or to `cabalProjectLocal`: ``` package postgresql-libpq flags: +use-pkg-config ``` Include a module like this one to include `openssl` in the linker arguments: ```nix { modules = [( {pkgs, ...}: final.lib.mkIf pkgs.stdenv.hostPlatform.isMusl { # The order of -lssl and -lcrypto is important here packages.postgrest.configureFlags = [ "--ghc-option=-optl=-lssl" "--ghc-option=-optl=-lcrypto" "--ghc-option=-optl=-L${pkgs.openssl.out}/lib" ]; })]; } ``` This PR also adds a "hackage quirk" for `postgrest` to that makes these changes for `postgrest` automatically when built it as a `tool` or with `hackage-package`. Unfortunately we do not have a good way to avoid the need make these changes.