At the start of the 2017–18 season, Haroun continued to establish himself in the starting eleven, playing in the midfield position, as well as, captain. It wasn't until on 19 August 2017 when he scored his first goal of the season, in a 2–1 win against KV Mechelen. Haroun started in every matches since the start of the season until he was suspended for one match. After serving a one match suspension, Haroun returned to the starting line–up, in a 1–0 win against K.A.S. Eupen on 18 November 2017. He then scored his second goal of the season, in a 1–0 win against Royal Excel Mouscron on 9 December 2017. Haroun then started for the next four matches for the side before suffering a calf injury that saw him missed one match. He then made his return to the starting line–up, starting the whole game, in a 1–1 draw against Charleroi on 27 January 2018. Haroun scored his third goal of the season, in a 2–0 win against K.A.S. Eupen on 3 May 2018. He appeared in six matches in the Europa League play-offs, as the club failed to earn a UEFA Europa League spot. At the end of the 2017–18 season, Haroun made thirty–three appearances and scoring three times in all competitions.