1 files changed, 5 insertions, 0 deletions
diff --git a/Lib/test/test_exception_hierarchy.py b/Lib/test/test_exception_hierarchy.py
index 8649596..43b4af8 100644
--- a/Lib/test/test_exception_hierarchy.py
+++ b/Lib/test/test_exception_hierarchy.py
@@ -150,10 +150,15 @@ class AttributesTest(unittest.TestCase):
             e = BlockingIOError(*args[:n])
             with self.assertRaises(AttributeError):
                 e.characters_written
+            with self.assertRaises(AttributeError):
+                del e.characters_written
         e = BlockingIOError("a", "b", 3)
         self.assertEqual(e.characters_written, 3)
         e.characters_written = 5
         self.assertEqual(e.characters_written, 5)
+        del e.characters_written
+        with self.assertRaises(AttributeError):
+            e.characters_written
 
 
 class ExplicitSubclassingTest(unittest.TestCase):