Aleksandar Mitrovic scored a late winner for Serbia as they pip Portugal to top spot in Group A.
Portugal took the lead through Renato Sanches's early goal, before Dusan Tadic equalised before the break.
Aleksandar Mitrovic, who didn't start the game, came on as a substitute at half time and scored the game winner in the 90th minute.
The result means Serbia win Group A and guarantee their spot at the 2022 World Cup, while Portugal must go into the play-offs - though they will be one of six seeded teams.