Intended to be able to RefCount an interface?

[weaselcat via Digitalmars-d-learn]

Thread title.

interface Itest{

}

class testclass : Itest{
}

void main()
{
    import std.typecons;
    auto test = RefCounted!Itest(new testclass());
}

If you change the refcounted to type testclass it doesn't compile 
because refcounted doesn't support classes.

Is this a bug, or intended?