diff --git a/src/darker/files.py b/src/darker/files.py
index 1b99a9ece..068d12c4b 100644
--- a/src/darker/files.py
+++ b/src/darker/files.py
@@ -3,7 +3,7 @@
 from __future__ import annotations
 
 import inspect
-from typing import TYPE_CHECKING, Collection, Optional, Tuple
+from typing import TYPE_CHECKING, Collection
 
 from black import (
     DEFAULT_EXCLUDES,
@@ -23,7 +23,7 @@
     from darker.formatters.base_formatter import BaseFormatter
 
 
-def find_pyproject_toml(path_search_start: Tuple[str, ...]) -> Optional[str]:
+def find_pyproject_toml(path_search_start: tuple[str, ...]) -> str | None:
     """Find the absolute filepath to a pyproject.toml if it exists"""
     path_project_root = find_project_root(path_search_start)
     path_pyproject_toml = path_project_root / "pyproject.toml"