Upon discovering that certain beliefs we hold are contingent on arbitrary features of our background, we often feel uneasy. I defend the proposal that if such cases of contingency anxiety involve defeaters, this is because of the epistemic significance of disagreement. I note two hurdles to our accepting this Disagreement Hypothesis. Firstly, some cases of contingency anxiety apparently involve no disagreement. Secondly, the proposal may seem to make our awareness of the influence of arbitrary background factors irrelevant in determining whether to revise our beliefs. I show that each of these problems can be successfully accommodated by the Disagreement Hypothesis.