diff --git a/pkgs/tools/package-management/nix/unstable.nix b/pkgs/tools/package-management/nix/unstable.nix
index ba0353e45078..a548a9f13bdd 100644
--- a/pkgs/tools/package-management/nix/unstable.nix
+++ b/pkgs/tools/package-management/nix/unstable.nix
@@ -5,11 +5,11 @@
 }:
 
 stdenv.mkDerivation rec {
-  name = "nix-1.6pre3220_fecad91";
+  name = "nix-1.7pre3252_792fd51";
 
   src = fetchurl {
-    url = "http://hydra.nixos.org/build/6038922/download/5/${name}.tar.xz";
-    sha256 = "0251b8cb7ad2a4974a9c8002c65f1c6e1b334be082d3dd2f085929594637f947";
+    url = "http://hydra.nixos.org/build/6500161/download/5/${name}.tar.xz";
+    sha256 = "f99c1996292ea1a20068f0a6d58d3dc4775f30fdd22cdd756ac4d749acb2c20e";
   };
 
   nativeBuildInputs = [ perl pkgconfig ];
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 8ab59423da23..6e533c023035 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -9920,13 +9920,10 @@ let
     stateDir = config.nix.stateDir or "/nix/var";
   };
 
-  nixUnstable = nixStable;
-  /*
   nixUnstable = callPackage ../tools/package-management/nix/unstable.nix {
     storeDir = config.nix.storeDir or "/nix/store";
     stateDir = config.nix.stateDir or "/nix/var";
   };
-  */
 
   nixops = callPackage ../tools/package-management/nixops { };