Run modprobe on startup
Check if you have a /etc/modules-load.d/wacom.conf file. If not, run this command:
sudo -i
echo wacom > /etc/modules-load.d/wacom.conf
This will create a configuration file ending in .conf and with content wacom.
Reboot and it will be loaded by systemd at boot time.
Just edit the file /etc/modules and add a new line with wacom.
You can reboot to check if it works.
If you do not have /etc/modules, try this one instead:
/etc/modules-load.d/modules.conf
Even if it should be not a problem since in Debian-like or Ubuntu-like ecc. they are symlinked.