Cat scratches walls...

Whenever my cat Spaz uses the litter box he scratches at the walls around it.He's ruining the paint.Why won't he scratch the litter?I've never seen another cat that has that behavior.Can you give me any suggestions on how to teach him to use the litter box properly?
Thanx

Try getting a covered litter box

He is just marking around his turf. They leave thier scent with the glands in their paws. If you can, I would just put some double back tape up or tape some aluminum foil where he scratches.

My litter box is in the bath tub and when one of my cats is done with digging and burying -- she scratches my shower liner for a few seconds - it looks like she's trying to get the litter out of her claws.