diff --git a/scratch/deepmind/part_two/shell.nix b/scratch/deepmind/part_two/shell.nix
index f1b02c4d2..606dd7167 100644
--- a/scratch/deepmind/part_two/shell.nix
+++ b/scratch/deepmind/part_two/shell.nix
@@ -1,4 +1,4 @@
-{ pkgs, ... }:
+{ pkgs ? import <nixpkgs> {}, ... }:
 
 pkgs.mkShell {
   buildInputs = with pkgs; [