This dataset provides replication data for an article on differential object marking in early Slavonic. The article uses extensive treebank data from the PROIEL and TOROT treebanks to track the much-debated rise of the animacy category in Russian, which in this article will be analysed as a change from at least partly definiteness-driven differential object marking in Old Church Slavonic via constructionally conditioned variation in Old East Slavonic to fully fledged animacy subgender marking in late Middle Russian. The change is interesting from a methodological point of view as well, since it requires us to annotate data through an ongoing change, and also since conventional treebank annotation is not enough to capture the conditions of the observed variation and change: annotation for semantics and information structure is necessary too. The article describes and defends a conservative approach to annotation in the face of change: the analysis that fits the first attested stage of a change is retained as long as possible.