Brazil global Gerson came off the bench to seize the best intention seven mins from time and preserve Jorge Sampaoli's side six points clear of the chasing % in 2d.
They remain nicely positioned to take France's handiest different automatic qualifying berth for next season's Champions League, but still have to play Lyon, Rennes and Strasbourg in 3 in their 4 last video games.
OM additionally travel to Feyenoord subsequent week for the first leg of their Europa Conference League semi-final.
"It became a difficult suit in opposition to an opponent who defended thoroughly, however I assume it was a deserved win," said Sampaoli.
"It's proper to preserve the distance with the ones chasing us because we have a difficult fixture list and those at the back of us also won so that put pressure on us to do the equal."
Rennes recovered from defeats with the aid of Monaco and Strasbourg over to demolish Lorient 5-zero at Roazhon Park.
Martin Terrier scored his 21st goal of the season shortly after Benjamin Bourigeaud had given Rennes the lead at Roazhon Park. Terrier is now simply one at the back of the league's pinnacle scorer Kylian Mbappe.
Captain Hamari Traore headed in a 3rd on the begin of the second one half, with Flavien Tait and Gaetan Laborde additionally on course after Rennes defender Nayif Aguerd turned into despatched off.
"Scoring twice within the first 20 mins gave us confidence," said Rennes educate Bruno Genesio.