diff --git a/pkgs/development/compilers/ghc/8.6.4.nix b/pkgs/development/compilers/ghc/8.6.4.nix
index d9c63edc9155..6cd7522bae87 100644
--- a/pkgs/development/compilers/ghc/8.6.4.nix
+++ b/pkgs/development/compilers/ghc/8.6.4.nix
@@ -155,7 +155,7 @@ stdenv.mkDerivation (rec {
   configureFlags = [
     "--datadir=$doc/share/doc/ghc"
     "--with-curses-includes=${ncurses.dev}/include" "--with-curses-libraries=${ncurses.out}/lib"
-  ] ++ stdenv.lib.optionals (libffi != null) ["--with-system-libffi" "--with-ffi-includes=${libffi.dev}/include" "--with-ffi-libraries=${libffi.out}/lib"
+  ] ++ stdenv.lib.optionals (libffi != null) ["--with-system-libffi" "--with-ffi-includes=${targetPackages.libffi.dev}/include" "--with-ffi-libraries=${targetPackages.libffi.out}/lib"
   ] ++ stdenv.lib.optional (targetPlatform == hostPlatform && !enableIntegerSimple) [
     "--with-gmp-includes=${targetPackages.gmp.dev}/include" "--with-gmp-libraries=${targetPackages.gmp.out}/lib"
   ] ++ stdenv.lib.optional (targetPlatform == hostPlatform && hostPlatform.libc != "glibc" && !targetPlatform.isWindows) [