A Musa Barrow goal earned tournament debutants Gambia a 1-0 win over Guinea in Bafoussam on Monday to seal their place in the quarter-finals.
Bologna forward Barrow collected a pass and slotted past Syli Nationale keeper Aly Keita in the 71st minute to clinch victory.
Gambia, the lowest-ranked side at the tournament at 150, will now face either hosts Cameroon or minnows Comoros in the last eight on Saturday.
Both teams finished a man down on Monday when Gambian Yusupha Njie was dismissed on 88 minutes with Guinean Ibrahima Conte following him down the tunnel in added time.
Gambia were forced to change both full-backs shortly before kick-off when Ibou Touray and Saidy Janko were ruled out by food poisoning.
The loss of captain and Liverpool midfielder Naby Keita through suspension would prove a major loss for Guinea who endured a frustrating end to the game.
Guinea thought they had equalised after 77 minutes when Conte pushed a cross into the net at the back post, but joy turned to frustration as his effort was ruled offside.
Substitute Njie was then sent-off for a second yellow card for Gambia and Guinea hit the woodwork twice in added time as well as having a penalty appeal turned down.