The choice between pronominal and zero form for objects in the Oceanic language Vera'a is investigated quantitatively in texts from two registers with discourse topics of three different ontological class memberships. Discourse topicality is found to predict best the choice between pronoun and zero, outranking the factors of ontological class membership, antecedent form, and antecedent function. Contrary to current models of referent tracking, antecedent distance does not show any effect at all. It is concluded that (a) discourse structure and activation are not universally the most significant factors in referential choice and (b) ontological class and discourse topicality can be teased apart through appropriate text sampling, and it is the latter that is most significant. This bears important implications for the grammaticalization of object agreement and the typology of differential object marking.