Nikolaus Rath added the comment: In that cases, maybe type(name, cls, clsdict) should actually raise an error if there's a metaclass with __prepare__ involved? Presumably that would break only code that was already broken, but it would convert previously hidden behavioral bugs into an explicit expressions raised at the right point. ---------- _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue18334> _______________________________________