diff --git a/pkgs/development/libraries/gtk+/3.x.nix b/pkgs/development/libraries/gtk+/3.x.nix
index b0409ee2808a..249f2651517f 100644
--- a/pkgs/development/libraries/gtk+/3.x.nix
+++ b/pkgs/development/libraries/gtk+/3.x.nix
@@ -41,7 +41,7 @@ stdenv.mkDerivation rec {
     ++ optional cupsSupport cups;
   #TODO: colord?
 
-  NIX_LDFLAGS = stdenv.lib.optionalString stdenv.isDarwin "-lintl";
+  NIX_LDFLAGS = optionalString stdenv.isDarwin "-lintl";
 
   # demos fail to install, no idea where's the problem
   preConfigure = "sed '/^SRC_SUBDIRS /s/demos//' -i Makefile.in";
@@ -60,7 +60,7 @@ stdenv.mkDerivation rec {
     "--enable-wayland-backend"
   ];
 
-  postInstall = ''
+  postInstall = optionalString (!stdenv.isDarwin) ''
     substituteInPlace "$out/lib/gtk-3.0/3.0.0/printbackends/libprintbackend-cups.la" \
       --replace '-L${gmp.dev}/lib' '-L${gmp.out}/lib'
   '';