Shaun Williams has triggered an extra 12 months on his Millwall contract after making his 15th Championship start of the season in Saturday’s 2-0 win at Reading.
The Irishman signed a new deal after promotion from League One and his terms included a clause extending his stay until the summer of 2019.
Williams would have hit the total sooner but for a knee injury which ruled him out for a couple of months.
Lions manager Neil Harris said: “Shaun has triggered an option in the contract which means we retain his services for next year. I’m absolutely delighted. His performances this year have been very, very impressive.
“He has given real stability and organisation to the team.
“His professionalism to fight back from injury so quickly was testimony to his desire to be on the football pitch.
“He showed on Saturday his importance to the squad when he went out on the pitch. He links the frontline and backline.
“I’m certainly looking forward to working with Shaun over the next 18 months and possibly beyond that.”