Anderlecht fell three points off the pace after they lost 2-1 at 10-man Standard Liege, while Club Brugge were held to a draw by Genk.
The defending champions were unbeaten in the Belgian first division this season with five wins and four draws but that record came to an end at the Stade Maurice Dufrasne on Sunday.
However, Anderlecht did hit the front through former Liverpool striker Milan Jovanovic on nine minutes.
French striker Frederic Bulot equalised for the hosts with his first goal of the campaign in the 27th minute before he netted the match winner with five minutes remaining in the first half.
Standard defender Reginal Goreux was shown a second yellow card after the hour mark but Ron Jans’ men managed to hold on for all three points.
League leaders Brugge played out a 1-1 stalemate with 10-man Genk but opened up a three point lead atop of the table.
Carlos Bacca opened the scoring for Brugge inside eight minutes and Genk’s problems were compounded when South African defender Calvin Ngongca received a straight red card after just 14 minutes.
But despite their numerical disadvantage, Genk never lost hope and restored parity eight minutes into the second half courtesy of Benjamin De Ceulaer.