Ah, because the empty `Persistent`s aren't initialised. You now can't just do a `Persistent::New` but you do have to start off with an empty `Persistent` in order to be able to assign to it. The `malloc` allocation above isn't going to suffice here. I'd probably change `proxy_container` to a `class` and `new` it and you ought to end up with what's needed (then `delete` instead of `free` of course). Is there another way here?