Africa Cup of Nations qualifiers Angola were held 1-1 at home by 10-man Gambia at the weekend in a warm-up match for the tournament in South Africa next month.
Foday Saidy was sent off after 10 minutes at the Estadio Ombaka in coastal city Benguela for handling the ball and Amaro converted the resulting penalty for the Black Antelopes.
Angola wasted several chances to stretch their lead and paid the price 18 minutes from time when Saloum Faal burst between two defenders and fired past goalkeeper Lama.
The Antelopes stage two more warm-up games this week -- four-time Cup of Nations winners Cameroon play in Lubango Wednesday and Rwanda provide the opposition in Luanda three days later.
Angola are seeded second in Group A at the Cup of Nations behind hosts South Africa and ahead of Morocco and surprise qualifiers Cape Verde Islands. They face the North Africans on January 19 in the first series of matches.