Frank de Boer's men boosted their hopes of a fourth successive title with a slender victory at De Adelaarshorst, midfielder Laase Schone's second-half strike proving the difference between the two sides.
The Denmark international found the bottom corner with a vicious long-range effort after his initial free-kick had been blocked by the wall.
Peter Bosz's side appeared set for a routine victory as defender Dan Mori headed home Christian Atsu's corner on the half-hour mark.
Heerenveen's chances of securing automatic qualification for the UEFA Europa League were dented with a 3-1 defeat at Cambuur.
Elvis Manu gave Cambuur the lead inside four minutes, before Bartholomew Ogbeche doubled the advantage a minute before the interval.
Jody Lukoki added a third midway through the second half to seal the points for Dwight Lodeweges' side, despite Alfred Finnbogason's late consolation.
Elsewhere, Groningen's clash with Twente was postponed due to a frozen pitch.
