In Spoken Continental French, the subject clitic il can in some cases be dropped – for example in certain impersonal construction (e.g. faut que ‘is necessary that’). This phenomenon is of particular interest in the context of claims that this variety of French is in fact a null subject language, with subject clitics acting as agreement affixes rather than true arguments (e.g. Roberge, 1990; Auger, 1994; Culbertson, 2010, among others). Under this view, the il in impersonals (and other constructions with less than fully referential subjects) is likewise an agreement marker, which can be dropped under some circumstances. Here we report the results of a controlled acceptability judgement task designed to probe features which affect the availability of il-drop. Our findings suggest that verb frequency, subcategorisation by the verb for a quasi-argument vs. true expletive, and modal vs. non-modal status influence il-drop. We discuss implications of this variation for an analysis of subject clitics as agreement affixes in Spoken French.