This paper investigates agreement mismatches in Dutch relatives. While the norm is that singular neuter nouns occur with the relative pronoun dat ‘that’, it is by now quite common to find neuter nouns combining with the relative pronoun die. A large Twitter corpus is used to study which linguistic variables make die ‘that’ in this context more likely. Lack of agreement between neuter noun and relative pronoun is very frequent in this corpus (37.5% of the cases, 46.8% if the preceding determiner is indefinite). Non-agreement is most common for nouns that are high in the animacy ranking, but it also occurs with other semantic classes, and there is quite a bit of lexical variation. Young, female users have a stronger tendency to use non-agreeing relative pronouns. Contrary to what previous work suggests, the paper does not find that users with a Moroccan or Turkish background have a stronger tendency towards non-agreement. A comparison of tweets with agreeing and non-agreeing pronouns and a comparison of the Twitter corpus with web data both suggest that non-agreement is characteristic of informal language use.