Colchester United learned their final opponent in the draw for the Papa Johns Trophy earlier with Brighton added to Southern Group A.
Brighton & Hove Albion complete the group along with the U's, Charlton Athletic and Gillingham, with dates for these games to be announced in due course.
It will be the third time in four seasons that Colchester United have taken on the Gills in the competition, having been narrowly beaten 1-0 here by the then League One side last season.
The U's will come up against Charlton Athletic for the first time since 2016, when Colchester took on the Addicks in the same competition.