Aguinaldo's late strike saw Recreativo do Libolo get their CAF Champions League campaign under way with a 1-0 win over ES Tunis on Sunday.
It was the first goal of the tournament after Leopards de Dolisie and Orlando Pirates drew a blank on the day before, and for a long while it looked as though Sunday's game would go the same way.
However, the Angolan side move to the top of Group B, after Aguinaldo headed home from a corner four minutes into injury time.
Their Tunisian opponents, who reached the final of the competition last year, were unable to reply and now sit bottom of the pile.
It means that Libolo are now seven games unbeaten in the competition, with their last defeat coming against Sunshine Stars in April 2012.
Libolo have won the last two Angolan Girabola titles, but are struggling in this season's campaign and sit in eighth place.
The two other sides in group B, Coton Sport and Sewe, play their first games in the competition on Saturday.