Weird Rack::Cache Output

gistfile1.txt

# Output from LiveHTTPHeaders
#
# NOTE: it looks like it's "forgetting" the Content-Type

http://localhost:4000/

GET / HTTP/1.1
Host: localhost:4000
User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.0.3) Gecko/2008092414 Firefox/3.0.3
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
X-lori-time-1: 1225471225984
If-Modified-Since: Fri, 31 Oct 2008 07:37:56 GMT
Cache-Control: max-age=0

HTTP/1.x 200 OK
Vary: Accept-Encoding
X-Content-Digest: fb263a2b888d04494d3370c99dadb3177ee181a7
Date: Fri, 31 Oct 2008 16:35:27 GMT
Content-Length: 502
Age: 298
X-Status: 200
Expires: Fri, 31 Oct 2008 16:40:25 GMT
Cache-Control: public,max-age=300
Connection: keep-alive
Server: thin 1.0.0 codename The Big
----------------------------------------------------------

# merb log
#
# [cache] info: GET /
# [cache] trace: cache hit (ttl: 226s)
# [cache] trace: delivering response ...