# Upgrade to 1.4## Minor BC Break: `Doctrine\Common\Cache\FileCache#$extension` is now `private`.If you need to override the value of `Doctrine\Common\Cache\FileCache#$extension`, then use thesecond parameter of `Doctrine\Common\Cache\FileCache#__construct()` instead of overridingthe property in your own implementation.## Minor BC Break: file based caches paths changed`Doctrine\Common\Cache\FileCache`, `Doctrine\Common\Cache\PhpFileCache` and`Doctrine\Common\Cache\FilesystemCache` are using a different cache paths structure.If you rely on warmed up caches for deployments, consider that caches generatedwith `doctrine/cache` `<1.4` are not compatible with the new directory structure,and will be ignored.