According to one-level physicalism, reality is exhausted by fundamental physical entities and properties. This position is sometimes defended on the basis of the truthmaker view of ontological commitment. Accordingly, physicalists can affirm higher-level truths without ontologically committing to any higher-level properties or states of affairs; fundamental physical states of affairs serve as truthmakers of all truths that have truthmakers, and a physicalist’s ontology should consist of nothing but the fundamental physical states of affairs and their constituents. In this paper, I (...) raise a problem for one-level physicalists who defend their views by appealing to the truthmaker view of ontological commitment. I argue that the truthmaker view faces certain puzzles the solutions of which clash with the main tenets of one-level physicalism. I conclude that either truthmaking is not a good guide to ontological commitment or one-level physicalism cannot be defended on the basis of the truthmaker view. (shrink)