I found a much better solution.

Run this in a terminal:
Code:

sudo nano /etc/default/grub

and change this line:
Code:

GRUB_CMDLINE_LINUX=""

to:
Code:

GRUB_CMDLINE_LINUX="acpi_backlight=vendor"

Save the file and run:
Code:

sudo update-grub

Now reboot. Your function keys for brightness should now work.