diff --git a/pkgs/development/compilers/gcc/4.9/default.nix b/pkgs/development/compilers/gcc/4.9/default.nix
index cf67d880a2cf..7e6c4a5fe4ff 100644
--- a/pkgs/development/compilers/gcc/4.9/default.nix
+++ b/pkgs/development/compilers/gcc/4.9/default.nix
@@ -32,7 +32,7 @@
 , gnat ? null
 , libpthread ? null, libpthreadCross ? null  # required for GNU/Hurd
 , stripped ? true
-, gnused ? null
+, CF ? null
 }:
 
 assert langJava     -> zip != null && unzip != null
@@ -47,8 +47,8 @@ assert cloog != null -> isl != null;
 # LTO needs libelf and zlib.
 assert libelf != null -> zlib != null;
 
-# Make sure we get GNU sed.
-assert stdenv.isDarwin -> gnused != null;
+# Make sure we get CoreFoundation
+assert stdenv.isDarwin -> CF != null;
 
 # The go frontend is written in c++
 assert langGo -> langCC;
@@ -290,10 +290,6 @@ stdenv.mkDerivation ({
     ++ (optionals (cross != null) [binutilsCross])
     ++ (optionals langAda [gnatboot])
     ++ (optionals langVhdl [gnat])
-
-    # The builder relies on GNU sed (for instance, Darwin's `sed' fails with
-    # "-i may not be used with stdin"), and `stdenvNative' doesn't provide it.
-    ++ (optional stdenv.isDarwin gnused)
     ;
 
   NIX_LDFLAGS = stdenv.lib.optionalString  stdenv.isSunOS "-lm -ldl";
@@ -304,14 +300,11 @@ stdenv.mkDerivation ({
     export CXXFLAGS_FOR_TARGET="-Wl,-rpath,$prefix/lib/amd64 $CXXFLAGS_FOR_TARGET"
     export CFLAGS_FOR_TARGET="-Wl,-rpath,$prefix/lib/amd64 $CFLAGS_FOR_TARGET"
   '' + stdenv.lib.optionalString stdenv.isDarwin ''
-    if SDKROOT=$(/usr/bin/xcrun --show-sdk-path); then
-      configureFlagsArray+=(--with-native-system-header-dir=$SDKROOT/usr/include)
-      makeFlagsArray+=( \
-       CFLAGS_FOR_BUILD=-F$SDKROOT/System/Library/Frameworks \
-       CFLAGS_FOR_TARGET=-F$SDKROOT/System/Library/Frameworks \
-       FLAGS_FOR_TARGET=-F$SDKROOT/System/Library/Frameworks \
-      )
-    fi
+    configureFlagsArray+=(
+      --with-sysroot="${stdenv.libc}"
+      --with-native-system-header-dir=/include
+      CFLAGS_FOR_BUILD=
+    )
   '';
 
   dontDisableStatic = true;
@@ -480,10 +473,10 @@ stdenv.mkDerivation ({
                                           ++ optionals javaAwtGtk [ gmp mpfr ]
                                           ++ optional (libpthread != null) libpthread)));
 
-  EXTRA_TARGET_CFLAGS =
-    if cross != null && libcCross != null
+  extraFlags =
+    (if cross != null && libcCross != null
     then "-idirafter ${libcCross}/include"
-    else null;
+    else "") + optionalString stdenv.isDarwin " -F${CF}/Library/Frameworks";
 
   EXTRA_TARGET_LDFLAGS =
     if cross != null && libcCross != null
diff --git a/pkgs/development/compilers/gcc/builder.sh b/pkgs/development/compilers/gcc/builder.sh
index dd77c67a023e..ee38fadf418b 100644
--- a/pkgs/development/compilers/gcc/builder.sh
+++ b/pkgs/development/compilers/gcc/builder.sh
@@ -23,8 +23,11 @@ if test "$noSysDirs" = "1"; then
 
         # Figure out what extra flags to pass to the gcc compilers
         # being generated to make sure that they use our glibc.
-        extraFlags="$(cat $NIX_CC/nix-support/libc-cflags)"
-        extraLDFlags="$(cat $NIX_CC/nix-support/libc-ldflags) $(cat $NIX_CC/nix-support/libc-ldflags-before)"
+        extraFlags="$(cat $NIX_CC/nix-support/libc-cflags) ${extraFlags}"
+        extraLDFlags="$(cat $NIX_CC/nix-support/libc-ldflags)"
+        if [ -e "$NIX_CC/nix-support/libc-ldflags-before" ]; then
+          extraLDFlags+=" $(cat $NIX_CC/nix-support/libc-ldflags-before)"
+        fi
 
         # Use *real* header files, otherwise a limits.h is generated
         # that does not include Glibc's limits.h (notably missing
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 7bbca479b1a4..1ed60e94358e 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -3849,6 +3849,8 @@ let
     isl = isl_0_11;
 
     cloog = cloog_0_18_0;
+
+    inherit (darwin) CF;
   }));
 
   gcc5 = lowPrio (wrapCC (callPackage ../development/compilers/gcc/5 {