Dotted cookie name as proxy_cache_key problem

[SergeyZh]

I'm trying to configure proxy cache for backend server and cookie name with user's login is long with dots (jetbrains.charisma.main.security.PRINCIPAL).
So my config is: 
proxy_cache_key  "$host$request_uri $cookie_jetbrains.charisma.main.security.PRINCIPAL";

And now proxied key is: 
KEY: youtrack.jetbrains.net/issue/RSRP-170140 .charisma.main.security.PRINCIPAL

I think there's some problem with parsing cookie name, because I don't see content of cookie in key name.
Nginx version is: 0.7.64

Can somebody explain me what should I set in proxy_cache_key to handle cookie name correctly, please ?

Thanks,
Sergey

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,62326,62326#msg-62326