The former Cheltenham shot-stopper has established himself as United's No 1, although he is currently sidelined with a thigh strain.
"We're delighted to have Shane for another year," Simon Grayson told the club's official website.
"He has done well since he came in and it's good to have that competition. Shane did well in pre-season, got his opportunity, and he took it with some good performances and some good saves.
"He is out at the moment but is making good progress. Casper has come in and he's done well and I'm pleased with the competition we have there because we have two good goalkeepers."