Ajax pulled off a victory over the Eredivisie's first-place side on Saturday, earning a 2-1 defeat of Zwolle at the Amsterdam ArenA.
The match was scoreless until the second half when the home side hit for two goals in the span of four minutes.
Thulani Serero opened the scoring in the 72nd minute before an own goal from Maikel van der Werff put Ajax two goals to the good.
Giovanni Gravenbeek pulled one back in the 89th minute, but it failed to spark a comeback for the visitors.
The top of the Eredivisie table becomes even tighter with PSV Eindhoven only managing a 2-2 draw at Twente on Saturday. Zwolle still resides at the summit on 13 points, but the club is followed closely by PSV on 12 points and Ajax on 11 points.
Also in the Dutch top flight on Saturday, Cambuur picked up a 2-0 win over Heracles while Den Haag's meeting with Vitesse was postponed due to a water- logged pitch.