Ajax, who are now two points clear of closest rivals Vitesse Arnhem, were stung by a 32nd-minute equaliser from Steve de Ridder, who broke clear of the defence and slotted past the goalkeeper.
The visitors had taken the lead eight minutes earlier through Daley Blind, with the Dutch international driving the ball home from 25 metres.
Ajax advanced to 44 points, ahead of Vitesse, who drew with fourth placed Feyenoord on Friday.
Twente Enschede are third on 40 points, but with a game in hand, after they came from behind to see off struggling SC Cambuur 3-1 at home with three second-half goals.
RKC Waalwijk climbed off the bottom of the table with a valuable 2-0 home win over PSV Eindhoven as Evander Sno scored twice in the second half.