diff --git a/Python/errors.c b/Python/errors.c
index 0f0b6ed..2a84c8d 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -575,7 +575,7 @@
 			goto failure;
 	}
 	/* Create a real new-style class. */
-	result = PyObject_CallFunction((PyObject *)&PyType_Type, "UOO",
+	result = PyObject_CallFunction((PyObject *)&PyType_Type, "sOO",
 				       dot+1, bases, dict);
   failure:
 	Py_XDECREF(bases);