Handbrake on Debian not aware of x265 despite installed

I am about to convert a lot of old MKV files encoded with x264 , which at the moment are un-downloadable, to more efficient HEVC (x265, H.265) format, using HandBrake software. My system being Debian Jessie 8.6, fully updated. I have installed handbrake and x265 packages from official repositories. The problem is, I can't seem to be able to choose x265 in HandBrake . On Linux Mint 18, there is no problem, it's just there. On Debian 8.6, there is a package called handbrake, on Linux Mint 18 I have added a PPA and installed handbrake-gtk. Versions seem to matter in this case: Debian: **0.9.9 (x86_64)** Mint: **0.10.5 (x86_64)**