The production of Atticist lexica in the 2nd century CE aimed to reproduce an idealised form of Attic Greek by prescribing specific morphological, lexical, and syntactic usages. However, the effect these prescriptions had on actual language usage has not yet been consistently investigated. In this paper, I will define a method for analysing the impact of Atticist norms on usage by adapting a framework proposed by Thomas (1991). I will then apply this framework to the study of one example: the infinitival complementation of μέλλω. While Markopoulos (2009) has shown that the use of the aorist infinitive in the complementation of μέλλω is a feature of low register, I will focus primarily on the use of the future infinitive, which is retained in this construction in classicising texts as a marker of high, learned register. I will then explore whether Atticist lexica contributed to fossilising the distribution of these infinitive types in the construction of μέλλω across different registers.