Add a value to a multi-valued field with REST Client?

I have had good success creating and editing tickets with RT::Client::REST
and my RT 4.0.17. However, I haven’t figured out how to add a value to a
custom field that accepts multiple values. When I update a ticket like so:

$ticket->cf(‘InventoryAsset’ => $aid); $ticket->store();

the ticket history shows that it first deletes the previous value before
adding the new value.

Is this possible or should I submit a wishlist bug to the queue at

thanks, Don