Index: Objects/typeobject.c
===================================================================
--- Objects/typeobject.c	(Revision 70582)
+++ Objects/typeobject.c	(Arbeitskopie)
@@ -6135,7 +6135,32 @@
 			   sanity checks and constructing a new argument
 			   list.  Cut all that nonsense short -- this speeds
 			   up instance creation tremendously. */
-			specific = (void *)type->tp_new;
+			PyObject *self = PyCFunction_GET_SELF(descr);
+			if (!self || !PyType_Check(self))
+				/* This should never happen because
+				   tp_new_wrapper expects a type for self.
+				   Use slot_tp_new which will call
+				   tp_new_wrapper which will raise an
+				   exception. */
+				specific = (void *)slot_tp_new;
+			else {
+				specific = ((PyTypeObject *)self)->tp_new;
+				/* Check that the user does not do anything
+				   silly and unsafe like object.__new__(dict).
+				   To do this, we check that the most derived
+				   base that's not a heap type is this type. */
+				PyTypeObject *staticbase = type->tp_base;
+				while (staticbase && (staticbase->tp_flags &
+							Py_TPFLAGS_HEAPTYPE))
+					staticbase = staticbase->tp_base;
+				if (staticbase && 
+				    staticbase->tp_new != specific)
+					/* Seems to be unsafe, better use
+					   slot_tp_new which will call
+					   tp_new_wrapper which will raise an
+					   exception if it is unsafe. */
+					specific = (void *)slot_tp_new;
+			}
 			/* XXX I'm not 100% sure that there isn't a hole
 			   in this reasoning that requires additional
 			   sanity checks.  I'll buy the first person to