The 20-year old Nigerian centre-back has penned a contract extension which will keep him at Stamford Bridge until 2018.
"I'm thrilled to sign a new contract with Chelsea and am really excited about the future," he told the club's official website.
"To play at such a fantastic club is a real honour for me and I'll be working incredibly hard to be successful.
"I've thoroughly enjoyed my time in England so far and can't wait to get going."
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