diff --git a/pkgs/development/ruby-modules/gem-config/default.nix b/pkgs/development/ruby-modules/gem-config/default.nix
index 76a044a56b2..1e1ee8bc797 100644
--- a/pkgs/development/ruby-modules/gem-config/default.nix
+++ b/pkgs/development/ruby-modules/gem-config/default.nix
@@ -22,7 +22,7 @@
 , pkgconfig , ncurses, xapian_1_2_22, gpgme, utillinux, fetchpatch, tzdata, icu, libffi
 , cmake, libssh2, openssl, mysql, darwin, git, perl, pcre, gecode_3, curl
 , libmsgpack, qt48, libsodium, snappy, libossp_uuid, lxc, libpcap, xorg, gtk2, buildRubyGem
-, cairo, re2, rake, gobjectIntrospection, gdk_pixbuf, zeromq, graphicsmagick
+, cairo, re2, rake, gobjectIntrospection, gdk_pixbuf, zeromq, graphicsmagick, libcxx
 }@args:
 
 let
@@ -69,7 +69,8 @@ in
   };
 
   capybara-webkit = attrs: {
-    buildInputs = [ qt48 ];
+    buildInputs = [ qt48 ] ++ stdenv.lib.optionals stdenv.isDarwin [ darwin.apple_sdk.frameworks.Cocoa ];
+    NIX_CFLAGS_COMPILE = stdenv.lib.optionalString stdenv.isDarwin "-I${libcxx}/include/c++/v1";
   };
 
   charlock_holmes = attrs: {