While grammatical context effects have been largely documented, their exact nature remains unclear. to determine the locus of these effects, we explored the priming in very strong grammatical contexts, that is, the priming of verbs by immediately preceding French pronominal subjects. In French, the first and second person plural pronouns are always associated with the same verbal inflections, creating very strong grammatical contexts. Participants made lexical decisions on targets (verb vs. pseudoverb) which were presented in three contexts: pronoun-congruent (nous grimpons, we climb), pronoun-incongruent (vous grimpons, you climb) or pseudoword control (zous grimpons, zous climb). Two experiments were conducted: one in the auditory modality and one in the visual modality. Grammatical context effects in the auditory modality did not vary as a function of the ISI, and no grammatical context effect was observed in the visual modality when the context was presented subliminally. These findings suggest that grammatical context effects operate at a post-lexical locus.