diff --git a/pkgs/tools/package-management/nix/default.nix b/pkgs/tools/package-management/nix/default.nix
index de6c1178221b..4359682d96a0 100644
--- a/pkgs/tools/package-management/nix/default.nix
+++ b/pkgs/tools/package-management/nix/default.nix
@@ -161,12 +161,12 @@ in rec {
 
   nixUnstable = (lib.lowPrio (common rec {
     name = "nix-1.12${suffix}";
-    suffix = "pre5655_cbc21691";
+    suffix = "pre5663_c7af84ce";
     src = fetchFromGitHub {
       owner = "NixOS";
       repo = "nix";
-      rev = "cbc216911dbda23c3bc050c969bc725fe60760ef";
-      sha256 = "0ynnk2m2n5pjmhy5gry90dy5k2wwy29v2wnq6zz32ak9zwz36x8r";
+      rev = "c7af84ce846a9deefa5b4db1b1bce1c091ca2a1e";
+      sha256 = "1sc6rkx0500jz4fyfqm7443s1q24whmpx10mfs12wdk516f0q8qh";
     };
     fromGit = true;
   })) // { perl-bindings = perl-bindings { nix = nixUnstable; }; };