Republic of Ireland Under-21s captain Jayson Molumby has signed a three-year contract extension at Brighton.
The 20-year-old has made 32 appearances so far this term on a loan deal at Millwall, but has now committed to Brighton until June 2023.
"The experiences Jayson has had in the tough environment of the Championship this season have really helped his overall game and we're delighted that he is committing himself to the club so he can continue his development when he comes back to us at the end of the season," said Brighton's technical director Dan Ashworth.
"We have watched him regularly this season and I know how pleased everyone at Millwall has been with his performances and his attitude.
"The new contract is a reward for his professionalism and hard work and I'm sure he will be looking to make a big impact when he comes back to the club."