auctex: prompt for label in theorem like environments

[nic . d . m . 1]

Hello!

Is there a way to configure auctex to prompt for a label name if you
insert a theorem environment?

I tried this in my .emacs file

(setq reftex-label-alist '(("theorem" ?h "thm:" "~\\ref{%s}" t
("theorem" "thm.") -3)))

(add-hook 'LaTeX-mode-hook
   (lambda ()
     (LaTeX-add-environments
      '("theorem" LaTeX-env-label))))

But auctex always generates a standard Label "thm:x", x integer.

I tried nil instead of t, also (nil . t) but nothing worked.

regards
nic