inconsistent behavior of caches_page method

ruby version : 1.8.6 rails version : 2.0.2 os : ubuntu 7.10

class StoreController < ApplicationController

    caches_page :index

    def index

        do something


    def expire

        expire_page :controller=>'store', :action=>'index'



when i visit: http://localhost:3000/store, a "RAILS_ROOT/public/ store.html" will appear

as i visit: http://localhost:3000/store/index, a "RAILS_ROOT/public/ store/index.html" will appear

the expire method in my class will delete the file "RAILS_ROOT/public/ store.html"

the problem is: {:controller=>'store',:action=>'index' }--->url_for method----->'/store' ,so expire_page will delete the file store.html.

if i don't use index action, it will not be a problem, but, anyone have better idea? thanks for the reply.