diff --git a/flake/dev-shell.nix b/flake/dev-shell.nix
index 6994787..227972d 100644
--- a/flake/dev-shell.nix
+++ b/flake/dev-shell.nix
@@ -8,7 +8,18 @@ _: {
     {
       devShells.default = pkgs.mkShell {
         inputsFrom = [ config.treefmt.build.devShell ];
-        shellHook = config.pre-commit.installationScript;
+        # Warn before pre-commit's installer fires: a set core.hooksPath
+        # makes it refuse with "Cowardly refusing to install hooks with
+        # core.hooksPath set". The fix is to unset, not to bypass.
+        shellHook = ''
+          if [ -n "$(git config --get core.hooksPath 2>/dev/null)" ]; then
+            echo "WARN: core.hooksPath is set to '$(git config --get core.hooksPath)'." >&2
+            echo "      pre-commit install will refuse. Unset it:" >&2
+            echo "        git config --unset core.hooksPath           # local" >&2
+            echo "        git config --global --unset core.hooksPath  # global" >&2
+          fi
+          ${config.pre-commit.installationScript}
+        '';
         packages = with pkgs; [
           nixfmt-rfc-style
           nil