diff --git a/testing/python/raises.py b/testing/python/raises.py
index b3fa0fc0e..f1f6ece4e 100644
--- a/testing/python/raises.py
+++ b/testing/python/raises.py
@@ -21,7 +21,9 @@ class TestRaises:
 
     def test_raises_does_not_allow_none(self):
         with pytest.raises(ValueError, match="Expected an exception type or"):
-            pytest.raises(expected_exception=None)
+            # We're testing that this invalid usage gives a helpful error,
+            # so we can ignore Mypy telling us that None is invalid.
+            pytest.raises(expected_exception=None)  # type: ignore
 
     def test_raises_does_not_allow_empty_tuple(self):
         with pytest.raises(ValueError, match="Expected an exception type or"):