I discuss the variation concerning agreement with coordinated subjects in Dutch dialects. I show that a verb or a complementizer in several variants of Dutch agrees with the first conjunct of a coordinated subject and in other variants with the coordinated subject as a whole. I argue that this variation can be accounted for by the interaction between the syntactic derivation and the post-syntactic morphological component. More specifically, I argue that syntax establishes an agreement relation with both the coordinated subject as a whole and the first conjunct of the coordinated subject. Subsequently, during the post-syntactic morphological derivation, one of these agreement relations will be overtly expressed on the Probe. The decision as to which one of the two relations is spelled out depends on the affix inventory of the language or dialect. More specifically, the subset principle is extended in such a way that, confronted with the situation in which a Probe is related to two Goals, an affix is inserted for the relation which results in the most specific agreement morphology. The analysis is extended to the typologically unrelated languages Irish and Arabic.