DELL XPS keyboard backlit not working

I have a new Dell XPS 13 Linux edition (this one) and immediately installed Linux Mint 18 on it, wiping the Ubuntu 14.04 which was shipped with the it.

I am really confident with it, only the backlight for the keyboard is not working. I have a keyboard light symbol on my F10 key but when I press it, nothing happens. All other features and all other media controls/media keys/screen brightness keys work. When clicking the battery icon in the Linux Mint taskbar, I see 2 controls, one for the keyboard lights brightness and one for the screen brightness. When I drag those bars, only the screen brightness is working again.

I also see the settings in /sys/class/leds/dell\:\:kbd_backlight/ (I think that's the config folder for it). The brightness file in this directory contains "1", so as I understand this correctly, this should theoretically work.

As I noted before I immediately installed Linux Mint on it, so I can't say whether it worked before. And this is really the only thing which is not working on the laptop.

I have obviously checked that my ultrabook has backlights with the product number on its back.

Do you have some tips so I can get this to work? Thanks in advance!