Athletic Bilbao have tied down Sabin Merino to a contract until 2019 with a €30m release clause.
The 24-year-old has signed the deal, Marca reports, with his previous terms due to expire at the end of the season.
Sabin graduated to Los Leones’ first team for the 2015-16 campaign after impressing with the B team, for whom he scored 21 goals in 80 games.
He has been a regular this season under Ernesto Valverde, making 17 La Liga appearances and scoring twice from midfield.