Theory of mind is a powerful cognitive ability: by the age of six, people are capable of accurately reasoning about others' beliefs and desires. An influential series of language understanding experiments by Keysar and colleagues, however, showed that adults systematically failed to take a speaker's beliefs into account, revealing limitations on theory of mind. In this paper we argue that these apparent failures are in fact successes. Through a minimal pair of replications comparing scripted vs. unscripted speakers, we show that critical utterances used by Keysar and colleagues are uncooperative: they are less informative than what a speaker would actually produce in that situation. When we allow participants to naturally interact, we find that listener expectations are justified and errors are reduced. This ironically shows that apparent failures of theory of mind are in fact attributable to sophisticated expectations about speaker behavior---that is, to theory of mind.