diff --git a/pkgs/os-specific/linux/cpufrequtils/default.nix b/pkgs/os-specific/linux/cpufrequtils/default.nix
index f2ee49ef75b2..cdf06103f683 100644
--- a/pkgs/os-specific/linux/cpufrequtils/default.nix
+++ b/pkgs/os-specific/linux/cpufrequtils/default.nix
@@ -1,16 +1,17 @@
 {stdenv, fetchurl, kernelHeaders, glibc, libtool, gettext}:
 
-assert stdenv.isLinux;
+assert stdenv.isLinux && stdenv.system != "powerpc-linux";
 
 stdenv.mkDerivation {
   name = "cpufrequtils-005";
+  
   src = fetchurl {
     url = http://www.kernel.org/pub/linux/utils/kernel/cpufreq/cpufrequtils-005.tar.gz;
     md5 = "100a8220a546ce61ce943d4107e67db9";
   };
 
   patchPhase = ''
-      sed -e "s@= /usr/bin/@= @g" \
+    sed -e "s@= /usr/bin/@= @g" \
       -e "s@/usr/@$out/@" \
       -i Makefile
   '';
diff --git a/pkgs/os-specific/linux/iputils/default.nix b/pkgs/os-specific/linux/iputils/default.nix
index 354419a4109c..14bd1b2b3239 100644
--- a/pkgs/os-specific/linux/iputils/default.nix
+++ b/pkgs/os-specific/linux/iputils/default.nix
@@ -1,6 +1,6 @@
 {stdenv, fetchurl, kernelHeaders, glibc}:
 
-assert stdenv.isLinux;
+assert stdenv.isLinux && stdenv.system != "powerpc-linux";
 
 stdenv.mkDerivation {
   name = "iputils-20020927";
diff --git a/pkgs/servers/mail/postfix/default.nix b/pkgs/servers/mail/postfix/default.nix
index 03fd33150e32..2d1499492305 100644
--- a/pkgs/servers/mail/postfix/default.nix
+++ b/pkgs/servers/mail/postfix/default.nix
@@ -1,22 +1,23 @@
-{stdenv, fetchurl, db4, glibc
-  , openssl
-  , cyrus_sasl
-}:
+{stdenv, fetchurl, db4, glibc, openssl, cyrus_sasl}:
 
-assert stdenv.isLinux;
+assert stdenv.isLinux && stdenv ? coreutils;
 
 stdenv.mkDerivation {
   name = "postfix-2.2.11";
+  
   src = fetchurl {
     url = ftp://ftp.cs.uu.nl/mirror/postfix/postfix-release/official/postfix-2.2.11.tar.gz;
     sha256 = "04hxpyd3h1f48fnppjwqqxbil13bcwidzpfkra2pgm7h42d9blq7";
   };
 
   installTargets = ["non-interactive-package"];
+  
   installFlags = [" install_root=$out "];
-  preInstall = "
+  
+  preInstall = ''
     sed -e '/^PATH=/d' -i postfix-install
-  ";
+  '';
+  
   postInstall = ''
     ensureDir $out
     mv ut/$out/* $out/
@@ -44,6 +45,8 @@ stdenv.mkDerivation {
   '';
 
   buildinputs = [db4 openssl cyrus_sasl];
+  
   patches = [./postfix-2.2.9-db.patch ./postfix-2.2.9-lib.patch];
+  
   inherit glibc;
 }
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 7f0aaa687951..d1c9348e2b15 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -5806,8 +5806,7 @@ let
   };
 
   postfix = import ../servers/mail/postfix {
-    inherit fetchurl stdenv db4 openssl cyrus_sasl;
-    glibc = stdenv.glibc;
+    inherit fetchurl stdenv db4 openssl cyrus_sasl glibc;
   };
 
   pulseaudio = import ../servers/pulseaudio {