A method of awarding a jackpot prize to a gaming device which contributes a percentage of turn-over to a jackpot prize pool comprises setting an accumulated turn-over trigger value for the gaming device, the accumulated turn-over trigger value set based on a jackpot prize pool trigger value which is, at least in part, randomly selected. Responsive to determining that the accumulated turn-over trigger value has been reached, the method further comprises awarding a prize to the gaming device.