Zambia and Tunisia failed to take advantage of Group D rivals Cameroon's shock African Nations Cup loss to Gabon as the two nations had to settle for a 1-1 draw in Lubango.
The Zambians will be most disappointed not to have got off to a winning start after largely dominating the game and seeing a late header from substitute Emmanuel Mayuka ruled out for offside.
The underdogs had made a fine start with the dangerous Rainford Kalaba striking the side-netting, while Tunisia looked a shadow of the side who had for a long time been one of the dominant forces on the continent.
Zambia took the lead in the 19th minute when Jacob Mulenga unselfishly played the ball back to James Chamanga in the box and his weak shot dribbled under Aymen Mathlouthi and into the net.
Kalaba had a shot blocked just past the half-hour and Zambia looked likely to add to their tally until Tunisia equalised out of nowhere in the 39th minute, Souheil Dhaoudadi slamming a cross by Youssef Msakni into the roof of the net.
The Tunisians started the second half stronger but Zamiba soon came back with Kampamba Chuntu missing a header in front of goal and Chamanga providing a constant thread.
Kalaba had the best chance in the 69th minute when he rose to meet a superb deep cross from Christopher Katongo but directed his free header into the ground when he should have scored.
Zambia pushed in the last 10 minutes with Mulenga driving a shot into the side-netting before Mayuka thought he had won it with his first touch only for the referee to deem otherwise.