diff --git a/pkgs/clan-cli/clan_cli/nix.py b/pkgs/clan-cli/clan_cli/nix.py
index 559b823..6d08a33 100644
--- a/pkgs/clan-cli/clan_cli/nix.py
+++ b/pkgs/clan-cli/clan_cli/nix.py
@@ -10,7 +10,7 @@ def nix_build_machine(
     machine: str, attr: list[str], flake_url: Path | None = None
 ) -> list[str]:
     if flake_url is None:
-        flake_url = get_clan_flake_toplevel()
+        flake_url = str(get_clan_flake_toplevel())
     payload = json.dumps(
         dict(
             clan_flake=flake_url,