From e0848503599f9cf2ce40ddb65cb99cca681ac75e Mon Sep 17 00:00:00 2001
From: Manuel Schlund <32543114+schlunma@users.noreply.github.com>
Date: Wed, 31 Jul 2024 17:14:43 +0200
Subject: [PATCH] Fix type hint for new mypy version (#2497)

---
 esmvalcore/_recipe/check.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/esmvalcore/_recipe/check.py b/esmvalcore/_recipe/check.py
index ac7b7f5bec..2978b74931 100644
--- a/esmvalcore/_recipe/check.py
+++ b/esmvalcore/_recipe/check.py
@@ -401,7 +401,7 @@ def _check_literal(
     *,
     step: str,
     option: str,
-    allowed_values: tuple[str],
+    allowed_values: tuple[None | str, ...],
 ) -> None:
     """Check that an option for a preprocessor has a valid value."""
     if step not in settings: