changing autofs to autofs4 in default.sel doesn't work

Hello everyone! I'm trying to change the default automounter package that is instaled by default, from "autofs" to "autofs4". I suppose that the way to do so is changing in default.sel (in the server repository) the line with "autofs" to "autofs4" (I also have re-create the packages database with create_pakage_descr, although I don't know whether this is really needed after changing .sel files). But this doesn't work! The old "autofs" is installed, not the desired "autofs4". Somebody knows what is the cause or how to solve the problem? Thanks in advance! ------------ Fermín