Manchester United have triggered a clause in Marouane Fellaini's contract that will keep him at Old Trafford until 2018.

Fellaini signed a four-year deal with the option of a further year when he joined from Everton for £27.5m in 2013.

United boss Jose Mourinho has activated the option despite uncertainty over the 29-year-old midfielder's future.

Fellaini was booed by his own fans last month but scored in the EFL Cup semi-final win against Hull on Tuesday.

The Belgium international ran to Mourinho to celebrate his goal in what seemed to be a show of recognition for the faith shown in him after a difficult period, which included giving away a costly penalty at Everton on 4 December.

Speaking after Tuesday's victory, Mourinho said: "He has a very strong mentality and has coped well.

"He knows he is a very important player for me."