diff --git a/shell/hooks/pre-commit.sh b/shell/hooks/pre-commit.sh
index 23776793..45efec25 100755
--- a/shell/hooks/pre-commit.sh
+++ b/shell/hooks/pre-commit.sh
@@ -7,15 +7,15 @@ else
   against=$(${git}/bin/git hash-object -t tree /dev/null)
 fi
 
-diff="git diff-index --name-only --cached $against --diff-filter d"
-
-mapfile -t all_files < <($diff)
-
 # Stash only unstaged changes, keeping staged changes
 old_stash=$(git rev-parse --quiet --verify refs/stash)
 git stash push --quiet --keep-index -m 'Unstaged changes before pre-commit hook'
 new_stash=$(git rev-parse --quiet --verify refs/stash)
 
+diff="git diff-index --name-only --cached $against --diff-filter d"
+
+mapfile -t all_files < <($diff)
+
 # Format staged files
 if ((${#all_files[@]} != 0)); then
   treefmt "${all_files[@]}" &&
diff --git a/treefmt.toml b/treefmt.toml
index c7c1710d..41ee3051 100644
--- a/treefmt.toml
+++ b/treefmt.toml
@@ -1,6 +1,7 @@
 [formatter.nix]
 command = "alejandra"
 includes = ["*.nix"]
+excludes = ["pkgs/_sources/generated.nix"]
 
 [formatter.prettier]
 command = "prettier"