Agreement By Correspondence ('ABC'; Rose & Walker 2004) is a framework originally proposed to analyze long-distance consonant harmony patterns. This paper shows that the same constraints used in ABC also predict dissimilation. Agreement in the ABC theory is based on surface correspondence: output consonants must correspond because they are similar. Since surface correspondence is based on similarity, constraints that penalize correspondence have the effect of favoring dissimilarity. Thus, dissimilation emerges from the interaction of constraints on surface correspondence, simply as a means of avoiding penalized correspondence (without involving the OCP or other specialized anti-similarity constraints). This mechanism explains an otherwise peculiar pattern of dissimilation found in Sundanese (Cohn 1992), in which rhotic consonants dissimilate only when correspondence between them is penalized by established constraints used in ABC to limit the scope of consonant harmonies.