refactor: Add Optional to type annotations

1 files changed, 2 insertions, 2 deletions

diff --git a/sphinx/transforms/i18n.py b/sphinx/transforms/i18n.py
index 8f6d37d8d..2a5d6f121 100644
--- a/sphinx/transforms/i18n.py
+++ b/sphinx/transforms/i18n.py
@@ -10,7 +10,7 @@
 
 from os import path
 from textwrap import indent
-from typing import TYPE_CHECKING, Any, Dict, List, Tuple, Type, TypeVar
+from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple, Type, TypeVar
 
 from docutils import nodes
 from docutils.io import StringInput
@@ -416,7 +416,7 @@ class Locale(SphinxTransform):
                                .format(old_xref_rawsources, new_xref_rawsources),
                                location=node)
 
-            def get_ref_key(node: addnodes.pending_xref) -> Tuple[str, str, str]:
+            def get_ref_key(node: addnodes.pending_xref) -> Optional[Tuple[str, str, str]]:
                 case = node["refdomain"], node["reftype"]
                 if case == ('std', 'term'):
                     return None