Oxford right-back Matt Bevans will remain with the U's for a further year after the club activated a clause in his contract.
Bevans made 12 appearances this season having arrived from Watford, initially as part of the U's development squad.
The 20-year-old told the club's official website: "I'm delighted to be staying at Oxford for another year. It's a great set-up here and I feel that I've really progressed as a player. Now I want to kick on and try to make even more first team appearances, although I know I've still got a lot to learn."
United's head coach Gary Waddock added: "We're very pleased to keep Matt on. He's progressed really well in his first year here and is one for the future."