Rails - Nov 2005 - cache_page throwing "undefined method merge" error

rails (0.14.2), OSX, webrick (right now - lighttpd in production)

I''m trying to cache pages with different file extensions and am having
a heck of a time.

This controller does nothing but display @cache.data (which can be XML or HTML)

Here''s the controller:

class DisplayController < ApplicationController
  caches_page :xml, :html
  session :off

  def xml
    @cache = Cache.find(params[:id])
    response.headers[''content-type''] =
@cache.browser_content_type
    #cache_page @cache.data,
"/display/xml/#{@params[''id'']}.xml"
  end

  def html
    @cache = Cache.find(params[:id])
    response.headers[''content-type''] =
@cache.browser_content_type
    #cache_page @cache.data,
"/display/html/#{@params[''id'']}.html"
  end

end

If I uncomment the cache_page lines I get these errors:

NoMethodError in
  Display#xml
undefined method `merge'' for /display/xml/1.xml

  NoMethodError in
  Display#html
undefined method `merge'' for /display/html/1.html

I need to set the file extension so that lighttpd sends out the
correct mime type.

Any ideas?