Anderlecht were awarded two spot kicks in the game, with defender Guillaume Gillet converting the first in his last game before moving to France but Matias Suarez missing out with the second when Anderlecht were already 2-1 up.
Stefano Okaka scored to give them a half-time lead but Westerlo equalised 10 minutes into the second half through Jens Cools.
Public demand led to Gillet taking the first penalty as the home crowd chanted his name after Anderlecht had been awarded the kick, marking an emotional end to his career at the club after signing for Nantes, who he joins next week.
The win lifted Anderlecht to 41 points with Gent now in their sights after the champions suffered a surprise defeat at Mechelen on Saturday.
Oostende could have gone third but lost 1-0 at Zulte-Waregem and stay fourth on 38 points, behind Club Bruges on 40. Steve de Ridder scored the game’s only goal just after the hour mark.
Earlier on Sunday, Standard Liege beat Mouscron-Peruwelz 3-0 with goals from Beni Badibanga, Mathieu Dossevi and Ivan Santini.
(Reporting by Mark Gleeson,; Editing by Pritha Sarkar)
