Recent studies have demonstrated that maintaining task-sets in working memory (WM) for prospective implementation can interfere with performance on an intervening task when the same stimulus requires incompatible responses in the ongoing versus the prospective task. This prospective task-set interference effect has previously been conceptualized as an obligatory process, resulting from instruction-based reflexivity (IBR). However, the extent to which strategic control can be exerted over interference in ongoing behavior from prospective task-sets held in WM has heretofore not been tested directly. To probe for strategic control over this effect, the authors conducted 3 experiments using a common inducer-diagnostic task design that manipulated the proportion compatibility of trials in the ongoing task. They hypothesized that if prospective task-set interference were malleable by control, participants would suppress the influence of the prospective set on ongoing processing when incompatible trials are frequent. Consistent with this prediction, the results show that prospective task-set interference is subject to modulation by strategic control such that the magnitude of interference is reduced, eliminated, or reversed in the presence of frequent incompatible trials. Thus, the influence on ongoing behavior of a prospective task-set held in WM is not obligatory, but subject to strategic control.