This article examines the impact of customer reward programs on the competitive outcome in duopolistic markets. We argue that loyalty discounts for repeat customers constitute a commitment device beneficial to suppliers rather than customers. Analyzing a two-period Bertrand model we show that the use of loyalty discounts makes it possible for duopolists to attain the fully collusive outcome in both periods. By offering generous loyalty discounts, the firms can credibly commit to refrain from second period poaching given that they attract enough customers in period one. Loyalty discounts invite firms to collude in the first period.