Lamine Kone has signed a new five-year contract at Sunderland after a proposed transfer to Everton was rejected in the summer transfer window.
The 27-year-old defender, who joined the Black Cats from Lorient in January, was linked with a £22m switch to the Toffees.
However, manager David Moyes reiterated on numerous occasions that Kone was not for sale, and now it has been confirmed that the Ivorian has committed himself to the club until 2021.
"Lamine is an important player for this club and I made that clear to him from the outset," Moyes told the club's official website. "He has only been playing in the Premier League since January, but in that time we have already seen what he is capable of.
"The challenge for Lamine now is to build on what has been a very positive introduction to English football and to continue to improve and grow as a player."
Meanwhile, Sunderland are yet to pick up a win in the Premier League after four matches.
