Wycombe Wanderers have confirmed that Jason McCarthy will remain with the club until January 3.
The 19-year-old initially joined the Chairboys from Southampton on a four-week loan deal last month.
However, having impressed manager Gareth Ainsworth with his performances since then, all parties have agreed to extend the centre-back's stay at Adams Park by a further two months.
"Jason had only played three minutes of professional football before he came here but he's slotted in extremely well and proved himself to be a very talented defender, as well as a popular and likeable member of the squad," Ainsworth told the club's official website.
"He's shown that he can adapt to the physical side of League Two football as well as play the ball out from the back and I'm delighted that he'll remain an important part of our squad for another eight weeks."
McCarthy made his only Premier League appearance for the Saints against Crystal Palace in December 2014.
