diff --git a/shell.nix b/shell.nix
index 3b33b7e..2e822a7 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,16 +1,17 @@
 # Shell for bootstrapping flake-enabled nix and home-manager, from any nix version
 { pkgs ? let
-    system = builtins.currentSystem or "Unknown system";
+    inherit (builtins) currentSystem pathExists fromJSON readFile;
 
     nixpkgs =
-      if builtins.pathExists ./flake.lock
+      if pathExists ./flake.lock
       then
       # If we have a lock, fetch locked nixpkgs
-        let lock = (builtins.fromJSON (builtins.readFile ./flake.lock)).nodes.nixpkgs.locked;
+        let
+          inherit ((fromJSON (readFile ./flake.lock)).nodes.nixpkgs) locked;
         in
         fetchTarball {
-          url = "https://github.com/nixos/nixpkgs/archive/${lock.rev}.tar.gz";
-          sha256 = lock.narHash;
+          url = "https://github.com/nixos/nixpkgs/archive/${locked.rev}.tar.gz";
+          sha256 = locked.narHash;
         }
       else
       # If not (probably because not flake-enabled), fetch nixos-unstable impurely
@@ -18,13 +19,16 @@
           url = "https://github.com/nixos/nixpkgs/archive/nixos-unstable.tar.gz";
         };
 
+    system = currentSystem;
+    overlays = [ ];
+
   in
-  import nixpkgs { inherit system; }
+  import nixpkgs { inherit system overlays; }
 , ...
 }:
 let
   # Enable experimental features without having to specify the argument
-  nix = (pkgs.writeShellScriptBin) "nix" ''
+  nix = pkgs.writeShellScriptBin "nix" ''
     exec ${pkgs.nixFlakes}/bin/nix --experimental-features "nix-command flakes" "$@"
   '';
 in