Nottingham City Council has added £10,000 to the reward fund for information leading to the killer of teenager Brendon Lawrence.
Brendon, 16, was shot in the street four years ago
The 16-year-old was shot dead on Watkins Street in St Ann's four years ago but his killers have remained free.
The new contribution to the reward will bring it to £20,000.
A candlelit vigil will be held on Tuesday on the street in his memory - as it has for the past three years.
Supt David Walker, who is in charge of policing in the area, said: "Anybody who has information, I am urging to ring me personally and bring the killers to justice."