AbstractMost linguistic theories of language offer analysis of agreement describing the rules and constraints involved in the computation and interpretation of this dependency. A good testing ground for theoretical accounts of agreement is mismatching patterns. In this article we focus on a mismatch available in the Spanish agreement system – Unagreement – in which there is a person mismatch in the realization of plural subject‐verb agreement. Unagreement seems to challenge both purely syntactic and lexicalist analyses of agreement, as the realization of this pattern cannot be carried out either on a strictly formal basis or by simply postulating a lexically‐driven asymmetry. We propose an approach that overcomes the limitations of existing analyses and that is able to successfully account for standard as well as non‐standard agreement patterns.