diff --git a/sphinx/highlighting.py b/sphinx/highlighting.py
index c5ac536ff84..76b657acee6 100644
--- a/sphinx/highlighting.py
+++ b/sphinx/highlighting.py
@@ -34,7 +34,7 @@
 if tuple(map(int, pygments.__version__.split('.')))[:2] < (2, 18):
     from pygments.formatter import Formatter
 
-    Formatter.__class_getitem__ = lambda cls, name: cls
+    Formatter.__class_getitem__ = lambda cls, name: cls  # type: ignore[attr-defined]
 
 logger = logging.getLogger(__name__)
 
diff --git a/tests/test_highlighting.py b/tests/test_highlighting.py
index 7149cf13c7e..1b8c2fbff73 100644
--- a/tests/test_highlighting.py
+++ b/tests/test_highlighting.py
@@ -11,7 +11,7 @@
 
 if tuple(map(int, pygments.__version__.split('.')))[:2] < (2, 18):
     from pygments.formatter import Formatter
-    Formatter.__class_getitem__ = lambda cls, name: cls
+    Formatter.__class_getitem__ = lambda cls, name: cls  # type: ignore[attr-defined]
 
 
 class MyLexer(RegexLexer):