The defender says he's determined to remain captain throughout the tenure of his current deal.
"Eleven years is a very good thing. But I'm not a conformist, I do not want to stop here, I want to go further. This is a special day," he told Real Madrid TV after marking 11 years with the club.
"I learned as a man and as a professional, and I believe as a footballer. Wearing the armband makes me proud and I hope to do even more during these four years.
"I am very happy and I hope to end my career here."