diff --git a/pkgs/development/compilers/gcc-4.6/builder.sh b/pkgs/development/compilers/gcc-4.6/builder.sh
index 8e1b3c8e4079..6cd64bc58f20 100644
--- a/pkgs/development/compilers/gcc-4.6/builder.sh
+++ b/pkgs/development/compilers/gcc-4.6/builder.sh
@@ -5,11 +5,6 @@ export NIX_FIXINC_DUMMY=$NIX_BUILD_TOP/dummy
 mkdir $NIX_FIXINC_DUMMY
 
 
-# libstdc++ needs this; otherwise it will use /lib/cpp, which is a Bad
-# Thing.
-export CPP="gcc -E"
-export CXXCPP="g++ -E"
-
 if test "$staticCompiler" = "1"; then
     EXTRA_LDFLAGS="-static"
 else
diff --git a/pkgs/development/compilers/gcc-4.6/default.nix b/pkgs/development/compilers/gcc-4.6/default.nix
index 71ca99b3c13a..03d3b235f109 100644
--- a/pkgs/development/compilers/gcc-4.6/default.nix
+++ b/pkgs/development/compilers/gcc-4.6/default.nix
@@ -153,13 +153,17 @@ stdenv.mkDerivation ({
 
   postPatch =
     if (stdenv.system == "i586-pc-gnu"
+        || (libcCross != null                  # e.g., building `gcc.hostDrv'
+            && libcCross ? crossConfig
+            && libcCross.crossConfig == "i586-pc-gnu")
         || (cross != null && cross.config == "i586-pc-gnu"
             && libcCross != null))
     then
       # On GNU/Hurd glibc refers to Hurd & Mach headers and libpthread is not
       # in glibc, so add the right `-I' flags to the default spec string.
+      assert libcCross != null -> libpthreadCross != null;
       let
-        libc = if cross != null then libcCross else stdenv.glibc;
+        libc = if libcCross != null then libcCross else stdenv.glibc;
         gnu_h = "gcc/config/gnu.h";
         i386_gnu_h = "gcc/config/i386/gnu.h";
         extraCPPDeps =
@@ -181,12 +185,18 @@ stdenv.mkDerivation ({
            echo "augmenting \`LIB_SPEC' in \`${gnu_h}' with \`${extraLibSpec}'..."
            sed -i "${gnu_h}" \
                -es'|LIB_SPEC *"\(.*\)$|LIB_SPEC "${extraLibSpec} \1|g'
+
+           echo "setting \`NATIVE_SYSTEM_HEADER_DIR' and \`STANDARD_INCLUDE_DIR' to \`${libc}/include'..."
+           sed -i "${gnu_h}" \
+               -es'|#define STANDARD_INCLUDE_DIR.*$|#define STANDARD_INCLUDE_DIR "${libc}/include"|g'
+           sed -i gcc/config/t-gnu \
+               -es'|NATIVE_SYSTEM_HEADER_DIR.*$|NATIVE_SYSTEM_HEADER_DIR = ${libc}/include|g'
         ''
     else if cross != null || stdenv.gcc.libc != null then
       # On NixOS, use the right path to the dynamic linker instead of
       # `/lib/ld*.so'.
       let
-        libc = if (cross != null && libcCross != null) then libcCross else stdenv.gcc.libc;
+        libc = if (libcCross != null) then libcCross else stdenv.gcc.libc;
       in
         '' echo "fixing the \`GLIBC_DYNAMIC_LINKER' and \`UCLIBC_DYNAMIC_LINKER' macros..."
            for header in "gcc/config/"*-gnu.h "gcc/config/"*"/"*.h