diff --git a/Objects/longobject.c b/Objects/longobject.c
index 4d886cd..ef3e242 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -3418,7 +3418,7 @@
 	0,					/* tp_setattro */
 	0,					/* tp_as_buffer */
 	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_CHECKTYPES |
-		Py_TPFLAGS_BASETYPE,		/* tp_flags */
+		Py_TPFLAGS_BASETYPE | Py_TPFLAGS_LONG_SUBCLASS,	/* tp_flags */
 	long_doc,				/* tp_doc */
 	0,					/* tp_traverse */
 	0,					/* tp_clear */