[Haskell-cafe] gtk2hs with old gtk2

I'm trying to build gtk2hs on debian/lenny, that is, with gtk2 v. 2.12 if I understand this correctly. I got the gtk2hs sources from darcs (I guess it's 0.11.0) and http://www.haskell.org/gtk2hs/ says "You need to specify -f-gtk_2_20 for Gtk+ 2.18 etc." I would love to, but where exactly? (When bootstrap.sh) Thanks - J.W.