diff --git a/pkgs/development/interpreters/lua-5/5.1.nix b/pkgs/development/interpreters/lua-5/5.1.nix
index b2ccc7fd642..adeaa9fae7b 100644
--- a/pkgs/development/interpreters/lua-5/5.1.nix
+++ b/pkgs/development/interpreters/lua-5/5.1.nix
@@ -29,7 +29,7 @@ stdenv.mkDerivation rec {
   configurePhase =
     if stdenv.isDarwin
     then ''
-    makeFlagsArray=( INSTALL_TOP=$out INSTALL_MAN=$out/share/man/man1 PLAT=macosx CFLAGS="-DLUA_USE_LINUX -fno-common -O2" LDFLAGS="" CC=clang )
+    makeFlagsArray=( INSTALL_TOP=$out INSTALL_MAN=$out/share/man/man1 PLAT=macosx CFLAGS="-DLUA_USE_LINUX -fno-common -O2" LDFLAGS="" CC="$CC" )
     installFlagsArray=( TO_BIN="lua luac" TO_LIB="liblua.5.1.5.dylib" INSTALL_DATA='cp -d' )
   '' else ''
     makeFlagsArray=( INSTALL_TOP=$out INSTALL_MAN=$out/share/man/man1 PLAT=linux CFLAGS="-DLUA_USE_LINUX -O2 -fPIC" LDFLAGS="-fPIC" )
diff --git a/pkgs/development/libraries/gmp/5.1.x.nix b/pkgs/development/libraries/gmp/5.1.x.nix
index 5bee2fe4336..e9495b796dd 100644
--- a/pkgs/development/libraries/gmp/5.1.x.nix
+++ b/pkgs/development/libraries/gmp/5.1.x.nix
@@ -22,7 +22,7 @@ stdenv.mkDerivation (rec {
     ++ (if cxx then [ "--enable-cxx"  ]
                else [ "--disable-cxx" ])
     ++ optional (cxx && stdenv.isDarwin) "CPPFLAGS=-fexceptions"
-    ++ optional stdenv.isDarwin "ABI=64 CC=clang"
+    ++ optional stdenv.isDarwin "ABI=64"
     ++ optional stdenv.is64bit "--with-pic"
     ;
 
diff --git a/pkgs/development/libraries/qt-4.x/4.8/default.nix b/pkgs/development/libraries/qt-4.x/4.8/default.nix
index 1679b4953e7..6c534f4220d 100644
--- a/pkgs/development/libraries/qt-4.x/4.8/default.nix
+++ b/pkgs/development/libraries/qt-4.x/4.8/default.nix
@@ -78,8 +78,6 @@ stdenv.mkDerivation rec {
       -translationdir $out/share/${name}/translations
     "
   '' + optionalString stdenv.isDarwin ''
-    export CXX=clang++
-    export CC=clang
     sed -i 's/QMAKE_CC = gcc/QMAKE_CC = clang/' mkspecs/common/g++-base.conf
     sed -i 's/QMAKE_CXX = g++/QMAKE_CXX = clang++/' mkspecs/common/g++-base.conf
   '';
diff --git a/pkgs/development/libraries/zlib/default.nix b/pkgs/development/libraries/zlib/default.nix
index 1b46c959448..0938e2a17a7 100644
--- a/pkgs/development/libraries/zlib/default.nix
+++ b/pkgs/development/libraries/zlib/default.nix
@@ -15,9 +15,7 @@ stdenv.mkDerivation rec {
 
   configureFlags = if static then "" else "--shared";
 
-  preConfigure = stdenv.lib.optionalString stdenv.isDarwin ''
-    export CC=clang
-  '' + ''
+  preConfigure = ''
     if test -n "$crossConfig"; then
       export CC=$crossConfig-gcc
       configureFlags=${if static then "" else "--shared"}
diff --git a/pkgs/tools/misc/getopt/default.nix b/pkgs/tools/misc/getopt/default.nix
index 84d15a18747..14bdb7889c9 100644
--- a/pkgs/tools/misc/getopt/default.nix
+++ b/pkgs/tools/misc/getopt/default.nix
@@ -7,6 +7,7 @@ stdenv.mkDerivation {
     url = http://tarballs.nixos.org/getopt-1.1.4.tar.gz;
     md5 = "02188ca68da27c4175d6e9f3da732101";
   };
-
-  buildFlags = stdenv.lib.optional stdenv.isDarwin [ "CC=clang" ];
+  preBuild = ''
+    export buildFlags=CC="$CC" # for darwin
+  '';
 }
diff --git a/pkgs/tools/package-management/nix/default.nix b/pkgs/tools/package-management/nix/default.nix
index e64bc329393..e659a1f1b03 100644
--- a/pkgs/tools/package-management/nix/default.nix
+++ b/pkgs/tools/package-management/nix/default.nix
@@ -22,8 +22,6 @@ stdenv.mkDerivation rec {
   postUnpack =
     '' export CPATH="${bzip2}/include"
        export LIBRARY_PATH="${bzip2}/lib"
-       export CXX=/usr/bin/clang++
-       export CXXFLAGS="-O3 -Wno-error=reserved-user-defined-literal"
     '';
 
   configureFlags =
@@ -34,7 +32,7 @@ stdenv.mkDerivation rec {
       --with-www-curl=${perlPackages.WWWCurl}/${perl.libPrefix}
       --disable-init-state
       --enable-gc
-      CFLAGS=-O3
+      CFLAGS=-O3 CXXFLAGS=-O3
     '';
 
   makeFlags = "profiledir=$(out)/etc/profile.d";
@@ -68,14 +66,10 @@ stdenv.mkDerivation rec {
   enableParallelBuilding = true;
 
   meta = {
-    description = "Powerful package manager that makes package management reliable and reproducible";
-    longDescription = ''
-      Nix is a powerful package manager for Linux and other Unix systems that
-      makes package management reliable and reproducible. It provides atomic
-      upgrades and rollbacks, side-by-side installation of multiple versions of
-      a package, multi-user package management and easy setup of build
-      environments.
-    '';
+    # due to builder args bug; see
+    # https://github.com/NixOS/nix/commit/b224ac15201c57b40ea855f5a98b1bd166c1c7f6
+    broken = stdenv.isDarwin;
+    description = "The Nix Deployment System";
     homepage = http://nixos.org/;
     license = stdenv.lib.licenses.lgpl2Plus;
     maintainers = [ stdenv.lib.maintainers.eelco ];
diff --git a/pkgs/tools/system/tree/default.nix b/pkgs/tools/system/tree/default.nix
index 51de5998069..eca8882643d 100644
--- a/pkgs/tools/system/tree/default.nix
+++ b/pkgs/tools/system/tree/default.nix
@@ -37,7 +37,7 @@ stdenv.mkDerivation {
       prefix=$out
       MANDIR=$out/share/man/man1
       ${systemFlags}
-      CC=clang
+      CC="$CC"
     )
   '';