AZ Alkmaar ended the weekend with a three-point lead in a congested Eredivisie title race after second-half goals from Rasmus Elm and Erik Falkenburg saw off De Graafschap.
Elm broke the deadlock directly from a corner four minutes after half-time and, after AZ rode out a spell of pressure for the hosts, Falkenburg made the game safe in injury time.
The result gives AZ a shaft of daylight at the summit, with just one point separating the teams from second to fifth place as the chase hots up.
De Graafschap's Rydell Poepon headed Soufian El Hassnaoui's cross wide early on but the first half failed to ever come to life thereafter.
The visitors had two chances around the midway point of the half after long balls out of defence, but Roy Beerens was foiled by keeper Yves de Winter and Brett Holman missed the target.
They needed just four minutes of the second half to make the breakthrough, though, as Sweden midfielder Elm's corner curled into the net untouched.
De Graafschap responded and from the hour mark onwards an equaliser appeared inevitable. Michael de Leeuw was first to threaten when his header was saved by Esteban Alvarado.
Gil Vermouth fired just wide from the edge of the box and Jordan Garcia-Calvete crossed for De Leeuw to again head past the post.
Poor defending let in Garcia-Calvete for a shot which was saved by Alvarado, and then a counter-attack led by Nenad Sreckovic ended with De Leeuw shooting over.
The hosts could not find the net, though, and Beerens crossed for Falkenburg to make it 2-0 two minutes into stoppage time.