Most 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.