diff --git a/pkgs/tools/package-management/nix/unstable.nix b/pkgs/tools/package-management/nix/unstable.nix
index ffc91922688b..1e98bb44ee20 100644
--- a/pkgs/tools/package-management/nix/unstable.nix
+++ b/pkgs/tools/package-management/nix/unstable.nix
@@ -4,11 +4,11 @@
 }:
 
 stdenv.mkDerivation rec {
-  name = "nix-0.16pre22611";
+  name = "nix-1.0pre23787";
 
   src = fetchurl {
-    url = "http://hydra.nixos.org/build/486717/download/4/${name}.tar.bz2";
-    sha256 = "1dazafq1flfyha9j5v31n46wh2bwg0iq59bwwgdk7n2xa8y7dz93";
+    url = "http://hydra.nixos.org/build/632513/download/4/${name}.tar.bz2";
+    sha256 = "01zn61ak6glyqpjxkzj8a7qw1vrfml1axky1jh1axkw6j35c34d7";
   };
 
   buildNativeInputs = [ perl ];
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 724b46898e11..d82fe06c06cf 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -6853,13 +6853,11 @@ let
     stateDir = getPkgConfig "nix" "stateDir" "/nix/var";
   };
 
-  nixUnstable = nixStable;
-  /*
   nixUnstable = callPackage ../tools/package-management/nix/unstable.nix {
     storeDir = getPkgConfig "nix" "storeDir" "/nix/store";
     stateDir = getPkgConfig "nix" "stateDir" "/nix/var";
   };
-  */
+
 
   # The SQLite branch.
   nixSqlite = lowPrio (makeOverridable (import ../tools/package-management/nix/sqlite.nix) {