Michael Ngadeu-Ngadjui struck the winner as Cameroon took control of Group A at the Africa Cup of Nations by coming from behind to beat Guinea-Bissau 2-1 in Libreville.
Four-time AFCON winners Cameroon looked to be heading for a shock defeat to competition debutants Guinea-Bissau until Ngadeu-Ngadjui added to Sebastien Siani's equaliser to put Hugo Broos' team two points clear at the top of the pool with one game left.
Guinea-Bissau took the lead after 13 minutes when Piqueti brilliantly surged from inside his own half and beat three players before slamming the ball beyond Fabrice Ondoa in the Cameroon goal.
However, the Indomitable Lions controlled possession and ground down their opponents, Siani drilling home from 20 yards in the 61st minute to set up a tense finale.
Ngadeu-Ngadjui, who made an important goal-line clearance with his side 1-0 down, completed the turnaround 17 minutes later when he guided Christian Bassogog's cutback into the bottom-right corner from just outside the box, putting Cameroon's fate in their own hands.
A draw against hosts Gabon in their final group match will be enough to secure Broos' side a place in the quarter-finals, while Guinea-Bissau will need to beat Burkina Faso to keep their campaign alive.
Some committed defending from Guinea-Bissau in the 12th minute saw Rudinilson Silva get his body in the way of Clinton N'Jie's shot from the left-hand side of the box, before Tomas Dabo blocked Vincent Aboubakar on the follow-up.
Despite that early pressure, Guinea-Bissau struck a surprise opener through a sensational solo counter-attack moments later.
Piqueti picked up the ball inside his own half and lobbed it over Collins Fai before racing away from Georges Mandjeck down the left. The winger then cut inside of Ngadeu-Ngadjui and drilled a powerful right-footed finish past Ondoa.
Cameroon controlled possession and, after N'Jie slammed a volley straight at Guinea-Bissau goalkeeper Jonas Mendes, Aboubakar spurned a glorious chance to pull them level in the 43rd minute when he scuffed a tame shot from Ambroise Oyongo's cutback into Mendes' arms.
Broos replaced N'Jie with Karl Toko Ekambi for the second half, while Piqueti made way for Idrissa Camara six minutes after the restart.
Guinea-Bissau had chances to increase their advantage, Frederic Mendy seeing his lob cleared off the line by Ngadeu-Ngadjui before Camara forced Ondoa into a save.
It proved costly after the hour mark when Siani rifled a low 20-yard shot with the outside of his right foot beyond Mendes.
And Cameroon snatched all three points through a fine finish from Ngadeu-Ngadjui with 12 minutes remaining.