diff --git a/pkgs/stdenv/generic/builder.sh b/pkgs/stdenv/generic/builder.sh
index fd4c17ca2519..6274200900cc 100644
--- a/pkgs/stdenv/generic/builder.sh
+++ b/pkgs/stdenv/generic/builder.sh
@@ -9,9 +9,15 @@ mkdir $out
 echo "$preHook" > $out/setup
 cat "$setup" >> $out/setup
 
+if [ "$withNixImpure" == 1 ]; then
+    # sed wants \&\& for a &&
+    niximpure='test -f /niximpure/impure.sh \&\& . /niximpure/impure.sh'
+fi
+
 sed -e "s^@initialPath@^$initialPath^g" \
     -e "s^@gcc@^$gcc^g" \
     -e "s^@shell@^$shell^g" \
+    -e "s^@niximpure@^$niximpure^g" \
     < $out/setup > $out/setup.tmp
 mv $out/setup.tmp $out/setup
 
diff --git a/pkgs/stdenv/generic/default.nix b/pkgs/stdenv/generic/default.nix
index ea101ddb075c..d85d9dfc06af 100644
--- a/pkgs/stdenv/generic/default.nix
+++ b/pkgs/stdenv/generic/default.nix
@@ -1,5 +1,6 @@
 { system, name ? "stdenv", preHook ? "", initialPath, gcc, shell
 , extraAttrs ? {}, overrides ? (pkgs: {})
+, withNixImpure ? false
 
 , # The `fetchurl' to use for downloading curl and its dependencies
   # (see all-packages.nix).
@@ -26,7 +27,7 @@ let
 
         setup = setupScript;
 
-        inherit preHook initialPath gcc shell;
+        inherit preHook initialPath gcc shell withNixImpure;
 
         propagatedUserEnvPkgs = [gcc] ++
           lib.filter lib.isDerivation initialPath;
diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index e30b0656e623..230694ccf35c 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -270,6 +270,7 @@ elif [ "$NIX_BUILD_CORES" -le 0 ]; then
 fi
 export NIX_BUILD_CORES
 
+@niximpure@
 
 ######################################################################
 # Misc. helper functions.
diff --git a/pkgs/stdenv/linux/default.nix b/pkgs/stdenv/linux/default.nix
index 224e749e6090..cae95615a446 100644
--- a/pkgs/stdenv/linux/default.nix
+++ b/pkgs/stdenv/linux/default.nix
@@ -95,6 +95,7 @@ rec {
       initialPath = [bootstrapTools] ++ extraPath;
       fetchurlBoot = fetchurl;
       inherit gcc;
+      withNixImpure = if platform ? nixImpure then platform.nixImpure else false;
       # Having the proper 'platform' in all the stdenvs allows getting proper
       # linuxHeaders for example.
       extraAttrs = extraAttrs // { inherit platform; };
@@ -270,7 +271,7 @@ rec {
     inherit system;
     
     preHook = commonPreHook;
-    
+
     initialPath = 
       ((import ../common-path.nix) {pkgs = stdenvLinuxBoot4Pkgs;})
       ++ [stdenvLinuxBoot4Pkgs.patchelf];
@@ -287,6 +288,8 @@ rec {
     shell = stdenvLinuxBoot4Pkgs.bash + "/bin/bash";
     
     fetchurlBoot = fetchurl;
+
+    withNixImpure = if platform ? nixImpure then platform.nixImpure else false;
     
     extraAttrs = {
       inherit (stdenvLinuxBoot3Pkgs) glibc;