How to auto-subscribe to virtual namespace/prefix?

[MRob]

In virtual namespace I can have:

namespace myvirt {
   location = blah
   prefix=Virtual/
   separator=/

   mailbox "My folder" {
     auto = subscribe
   }
}

And i see email clients successful display subscribed "My folder" but 
the top-level prefix "Virtual/" is not subscribed. I see the Virtual/ 
prefix available as a noselect folder in the list of unsubscribed 
folders and if I manual subscribe to it, folder tree display is perfect.

So how can i also make auto-subscription to the "Virtual/" prefix 
noselect folder?