The continental minnows dented Chipolopolo's AFCON hopes with a shock 2-1 triumph in Bissau on Sunday.
2019 ScheduleAll times ET
Chipolopolo saw off their opponents to move up to four points in AFCON qualifying Group K.
A stunning solo goal from Piqueti was not enough for Guinea Bissau as Cameroon came from behind to win 2-1 and take pole position at African Nations.
Gabon's hosting of the 2017 African Nations Cup has not been universally popular, and a shock 1-1 draw on day one hammered home their malaise.