Express FC condemned Uganda Premier League leaders Vipers SC to a 1-0 loss during Friday's encounter at St Mary's Stadium, Kitende.
John Byamukama scored the only goal that separated two of this season's clear title contenders to ensure the Red Eagles went home with three points.
Ceasar Manzoki of Vipers was yellow-carded in the 13th minute for a rough challenge on the opponent when the game was picking up speed.
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Paul Mucureezi could have opened the score in the 28th minute but he sent his effort over the bar after he had been put through on goal by Disan Galiwango.