Algeria inflicted a rare home defeat on Cameroon as the 2019 African champions took a crucial 1-0 lead from the first leg of their 2022 World Cup play-off.
Playing in Douala, where Cameroon have been unbeaten since losing a Nations Cup qualifier in 2000, veteran Islam Slimani's winner handed Algeria coach Djamel Belmadi the perfect 46th birthday present.
Five minutes before the break, the former Leicester City striker rose to meet Youcef Belaili's free-kick and power a header past Ajax goalkeeper Andrè Onana.
The Desert Foxes - bidding to reach a fifth World Cup - host Cameroon, who have been to more World Cups (seven) than any other African side, in the return leg on Tuesday.
The Algerians, whose 35-match unbeaten run ended at recent Africa Cup of Nations in Cameroon, resumed their form heading into that tournament when showing steely resolve to keep the hosts at bay.
Fifty thousand supporters had packed the Japoma stadium, where Algeria had lost two matches and drawn one in their disappointing Nations Cup display.
Source: BBC Sports