diff --git a/shell.nix b/shell.nix
index 0c7624a..ba568b5 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,12 +1,12 @@
 let
-  pkgs = import <nixpkgs> { }; # pin the channel to ensure reproducibility!
+  pkgs = import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/747927516efcb5e31ba03b7ff32f61f6d47e7d87.zip") { }; # pin the channel to ensure reproducibility!
 in
 pkgs.haskellPackages.developPackage {
   root = ./.;
   withHoogle = true;
   modifier = drv:
   pkgs.haskell.lib.addBuildTools drv (
-    (with pkgs; [ hlint haskell-language-server ghc jasmin ])
+    (with pkgs; [ hlint haskell-language-server ghc jasmin llvm ])
     ++
     (with pkgs.haskellPackages; [ 
       cabal-install