diff --git a/home-manager/common.nix b/home-manager/common.nix
index 0e10a51..0d84f09 100644
--- a/home-manager/common.nix
+++ b/home-manager/common.nix
@@ -13,12 +13,14 @@ inputs: all: {
     enable = lib.mkDefault true;
     nix-direnv.enable = lib.mkDefault true;
     stdlib = ''
-      : ''${XDG_CACHE_HOME:=$HOME/.cache}
+      : "${XDG_CACHE_HOME:="${HOME}/.cache"}"
       declare -A direnv_layout_dirs
       direnv_layout_dir() {
-          echo "''${direnv_layout_dirs[$PWD]:=$(
-              echo -n "$XDG_CACHE_HOME"/direnv/layouts/
-              echo -n "$PWD" | shasum | cut -d ' ' -f 1
+          local hash path
+          echo "${direnv_layout_dirs[$PWD]:=$(
+              hash="$(sha1sum - <<< "$PWD" | head -c40)"
+              path="${PWD//[^a-zA-Z0-9]/-}"
+              echo "${XDG_CACHE_HOME}/direnv/layouts/${hash}${path}"
           )}"
       }
     '';