A longstanding question in sociolinguistics is whether the social patterning of a variant is consistent across linguistic environments. It is traditionally assumed that language-external (i.e. social) factors do not interact with language-internal factors (characteristics of the linguistic environment surrounding the varying item) in the conditioning of variation (Labov 1993, Labov 2001:28, Labov 2010:265), but this has largely gone untested with modern statistical methods and large data sets. In this paper, we report on a study of a single variable alternation in English — between ‘of’ and Ø, henceforth “‘of’-variation” — that is instantiated in several distinct linguistic environments. We find that its social patterning differs by environment, suggesting a counterexample to the proposed independence of external and internal conditioning factors.