[Zope] REQUEST.unset('property') in DTML ?

Hi all, I was read in archives about REQUEST.unset to unset property. But published patch is little older (1999) and my Zope 2.5.1 is totally different than that patch. Zope does not protest when I save DTML method with REQUEST.unset('property'), but when I access page, then Zope give me error that unknown keyword unset. Note that pythonic :) equivalent to unset <dtml-call "del REQUEST.other['property']"> could not be saved to server (error). It is possible to delete previously <dtml-call "REQUEST.set('property')"> in DTML ? Thanks a lot, J. Lukesh