sort thread by last-mail received

[Globe Trotter]

Hi,

Looking at: http://www.mutt.org/doc/manual/manual.html#sort, it seems to me that I should simply 

set sort=threads
set sort_aux=reverse-date-received

However, what I get is the threads, correctly, but the ones with most recent messages do not come up first. I want the threads with most recent activity coming up first. Can this be done in mutt? (I do not want reverse_threads.)

Sorry if my question is unclear.

Thanks,
GT