Symfony 2 - 当缓存设置为public时，文件未被gzip压缩

I have strange behaviour in prod env. I set in php.ini

zlib.output_compression = On
zlib.output_compression_level = 6

On http://mysite.dev/ everything working fine:

Accept-Ranges   bytes
Age 0
Cache-Control   public, s-maxage=60
Connection  keep-alive
Content-Encoding    gzip
Content-Type    text/html; charset=UTF-8

but on production http://mysite.prod/ it doesn't:

Age 0
Cache-Control   public, s-maxage=60
Connection  keep-alive
Content-Length  2951
Content-Type    text/html; charset=UTF-8

Have no idea where to search a solution.

Edit:

Found the problem, i have enabled AppCache.php wraper in web/app.php:

require_once __DIR__.'/../app/AppKernel.php';
require_once __DIR__.'/../app/AppCache.php';

$kernel = new AppKernel('prod', false);
$kernel->loadClassCache();
$kernel = new AppCache($kernel);

Is this possible that cached files stored in app/cache/prod are not parsed by php (ommit zlib.output_compression)?