Marseille set up a clash with bitter rivals Paris Saint-Germain in the last 16 of the French Cup after edging out third-tier Rouen on Wednesday thanks to a goal that should never have stood.
Elie Baup's side were already leading in Normandy courtesy of a Mathieu Valbuena free-kick when they were incorrectly awarded a second goal.
A hanging cross from the right wing from recent signing Modou Sougou was spilled on the line by Rouen 'keeper Theo Defourny.
He appeared to stop the whole ball from crossing the line, but the officials thought otherwise and gifted the Ligue 1 club a 2-0 lead.
Television replays suggested that Defourny was hard done by and the goalkeeper was booked for protesting the decision.
Rouen had knocked out top-flight Ajaccio in the previous round and they never gave up against a Marseille side who lie third in Ligue 1, with Remy Dugimont reducing the deficit late on after Steve Mandanda had failed to hold a Julien Jahier header.
However, they could not find an equaliser as Sougou's disputed goal ultimately decided this tie, which was postponed last week after a major gas leak in the Normandy city.
Marseille will now face PSG in the next round, with the tie scheduled to take place just days after the clubs meet in Ligue 1 at the Parc des Princes on February 24.
The sides also met in the last 16 of the League Cup earlier this season, with PSG winning 2-0 in the capital on that occasion.