diff --git a/pkgs/development/libraries/gss/default.nix b/pkgs/development/libraries/gss/default.nix
index a748d9582695..0cc6a07e0839 100644
--- a/pkgs/development/libraries/gss/default.nix
+++ b/pkgs/development/libraries/gss/default.nix
@@ -1,9 +1,9 @@
 { stdenv, fetchurl
-
-# Optional Dependencies
-, shishi ? null
+, withShishi ? !stdenv.isDarwin, shishi ? null
 }:
 
+assert withShishi -> shishi != null;
+
 stdenv.mkDerivation rec {
   name = "gss-1.0.3";
 
@@ -12,16 +12,16 @@ stdenv.mkDerivation rec {
     sha256 = "1syyvh3k659xf1hdv9pilnnhbbhs6vfapayp4xgdcc8mfgf9v4gz";
   };
 
-  buildInputs = [ shishi ];
+  buildInputs = stdenv.lib.optional withShishi shishi;
 
   configureFlags = [
-    "--${if shishi != null then "enable" else "disable"}-kereberos5"
+    "--${if withShishi != null then "enable" else "disable"}-kereberos5"
   ];
 
   doCheck = true;
 
   # Fixup .la files
-  postInstall = stdenv.lib.optionalString (!stdenv.isDarwin && shishi != null) ''
+  postInstall = stdenv.lib.optionalString withShishi ''
     sed -i 's,\(-lshishi\),-L${shishi}/lib \1,' $out/lib/libgss.la
   '';