Economic growth is often in conflict with environmental goals. Biodiversity offsetting attempts to resolve this conflict by requiring industries to compensate for the biodiversity loss they cause, by generating an equivalent biodiversity gain elsewhere. Offsets for environmental impacts are increasingly being seen as a way to help meet preexisting conservation targets, such as those relating to the establishment and management of protected areas. We examine how using offsets to meet a state or organization's genuine commitments, which are not contingent on the offsets, results in no additional conservation benefit. In this case, either the offset or the preexisting commitment is invalid. For example, the use of offsets to meet commitments under the Convention on Biological Diversity requires an admission that those commitments would otherwise not be met. This interaction between international agreements around protected areas and offset policy can generate perverse incentives, which must be carefully managed to avoid poor conservation outcomes. We propose separate accounting for conservation gains generated using offsets, and that future conservation agreements and targets should explicitly separate commitments met using offset gains from those which are not reliant on equivalent losses.