std.concurrency : sending immutable classes

[Dicebot]

Minimized repro:

import std.variant;

class A {}

void main()
{
     Variant v = new immutable A();
     auto x = v.get!(immutable A)();  // triggers assert
}

One simple question - did this ever work? :) Because passing 
immutable aggregate messages is sometimes sold as one of "proper" 
usage scenario of std.concurrency and if it was never actually 
implemented, that is damn sad. I have started to investigate this 
scenario because of question on topic in #d @ freenode.