diff --git a/Objects/descrobject.c b/Objects/descrobject.c
index 4971b4c..0324ac2 100644
--- a/Objects/descrobject.c
+++ b/Objects/descrobject.c
@@ -975,7 +975,7 @@
 	PyObject_GenericGetAttr,		/* tp_getattro */
 	0,					/* tp_setattro */
 	0,					/* tp_as_buffer */
-	Py_TPFLAGS_DEFAULT,			/* tp_flags */
+	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /* tp_flags */
  	getset_doc,				/* tp_doc */
  	0,					/* tp_traverse */
  	0,					/* tp_clear */