Permalink and cache page

I made the example in railscasts 117
for clean urls and static pages and it worked fine.

After that I wanted to do a simple page cache with pages_cache and
expire_page (as in railscasts 89
The page_cache works fine and it creates the pages in public folder,
but the expire_page doesn't work for the permalink, it works
for /:action/:id url, so I can't update the pages. I am thinking of
doing it manually (delete the html file with plain ruby when a page is
updated, instead of expire_page) or to make a button to enable/disable
the cache... or is there a better way instead of this to make the
expire_page work?