diff --git a/default.nix b/default.nix
index 57b326437ec..3923cb9592b 100644
--- a/default.nix
+++ b/default.nix
@@ -1,10 +1,12 @@
 let
 
-  configFileName =
-    let env = builtins.getEnv "NIXOS_CONFIG"; in
-    if env == "" then /etc/nixos/configuration.nix else env;
+  fromEnv = name : default :
+    let env = builtins.getEnv name; in
+    if env == "" then default else env;
+  configuration = import (fromEnv "NIXOS_CONFIG" /etc/nixos/configuration.nix);
+  nixpkgsPath   =         fromEnv "NIXPKGS"      /etc/nixos/nixpkgs;
 
-  system = import system/system.nix {configuration = import configFileName;};
+  system = import system/system.nix { inherit configuration nixpkgsPath; };
 
 in
 
diff --git a/installer/nixos-rebuild.sh b/installer/nixos-rebuild.sh
index b8deee2f18e..06a7a4d39fc 100644
--- a/installer/nixos-rebuild.sh
+++ b/installer/nixos-rebuild.sh
@@ -5,6 +5,7 @@
 NIXOS=${NIXOS:-@defaultNIXOS@}
 NIXPKGS=${NIXPKGS:-@defaultNIXPKGS@}
 NIXOS_CONFIG=${NIXOS_CONFIG:-/etc/nixos/configuration.nix}
+export NIXPKGS # must be exported so that a non default location is passed to nixos/default.nix
 
 showSyntax() {
     # !!! more or less cut&paste from