Skill spawning fire with /fill doesn't work

Hello,
I created a boss using a skill calling a /fill to cast a fire square around him. So..


Skills:
- message{m="<mob.name><&co> Fiiiireee..."} @PlayersInRadius{r=30}
- delay 60
- command{c="fill ~2 ~ ~2 ~-2 ~ ~-2 fire"} @Self
- effect:explosion @Self
- message{m="<mob.name><&co> Ring!"} @PlayersInRadius{r=30}
- delay 100
- (another command to extinguish but whatever)

The problem is, my console tells me "Cannot place blocks outside of the world". Now, I know this could...

Skill spawning fire with /fill doesn't work