Athletic Bilbao have confirmed that Iker Muniain has signed a new contract with the club.
The 22-year-old's previous deal at the San Mames still had two years left to run before it expired.
However, he has now agreed to extend his terms until the summer of 2019, with a buyout clause of £31.5m also included.
The playmaker, who has risen through the ranks at Bilbao, is currently undergoing rehabilitation on the cruciate knee ligament injury that he suffered late last season.