Chelsea's teenage prospect Nathan Ake has signed a long-term deal.
The 18-year-old, who can play in defence or at the base of the midfield, is now contracted to the club until the summer of 2018.
Ake, a Holland youth international, broke into the first-team squad last season and finished the campaign with six appearances.
He told the club website: "I'm very happy that Chelsea is rewarding me with a new contract for my effort and development the last years.
"I would like to thank everybody at the club for everything they did for me. Thanks to them I have come so far. I won't let them down and will keep on working as hard as I can."