diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index fbff31b..4fe4d10 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -7971,7 +7971,8 @@
     PyObject_GenericGetAttr, 		/* tp_getattro */
     0,			 		/* tp_setattro */
     &unicode_as_buffer,			/* tp_as_buffer */
-    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /* tp_flags */
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | 
+        Py_TPFLAGS_UNICODE_SUBCLASS,	/* tp_flags */
     unicode_doc,			/* tp_doc */
     0,					/* tp_traverse */
     0,					/* tp_clear */