SPDY not forwarding Accept-Encoding headers for Firefox

Firefox is claiming to be sending the Accept-Encoding header (specifically "Accept-Encoding: gzip, deflate") but somewhere it appears to be dropped. I don't see it show up in the logs with http.* debug on. Here is what TS sees:

+++++++++ Incoming Request +++++++++
– State Machine Id: 0
GET
http://origin.example.com/
HTTP/1.1
accept: text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8
accept-language: en-US,en;q=0.5
cookie: <cookies>
dnt: 1
user-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:32.0)
Gecko/20100101 Firefox/32.0
Host: example.com