diff --git a/Lib/test/test_gettext.py b/Lib/test/test_gettext.py
index e517c9d5c2a53f..dd00e8498962fe 100644
--- a/Lib/test/test_gettext.py
+++ b/Lib/test/test_gettext.py
@@ -402,7 +402,7 @@ def test_plural_context_forms_null_translations(self):
             numbers_only=False)
 
 
-class PluralFormsInternalTestCase:
+class PluralFormsInternalTestCase(unittest.TestCase):
     # Examples from http://www.gnu.org/software/gettext/manual/gettext.html
 
     def test_ja(self):