Puppy is "angry peeing" when we crate him on the weekends.

9 month old puppy is crated during the week. He gets a walk halfway through the day and someone is usually home around 4. He has no issues with accidents during that time.
When we leave him for a short amount of time to go to breakfast or the store on the weekend, he pees in the crate. He always has a walk before he's crated so he should be peeing in there!
Is he simply mad that we're leaving him on a weekend? He's a smart little dude. He notices out routines and knows when we're getting ready to go. How do we stop him from angry peeing?