Keyword not changed when ticket changed Queue

I have just noticed that when a ticket with keyword set changes from one
queue to another, the old keyword remains in the ObjectKeywords table
and the same ticket in the new queue does not carry that keyword with
it. When updating keywords for the same ticket in the new queue, it
will add a new entry, but not updating the old one. Is this the way you
designed it, or is this a bug?

Nobel