Social conventionalism — the position that social conventions governing language use determine or constitute the meanings of our words — has faced two major problems. The first is the Agreement Problem: how could speakers agree to use words in certain ways without already speaking meaningfully? The second is the Novelty Problem: how can conventions fix the meanings of innovative uses of words? David Lewis famously responded to the Agreement Problem but his account flounders on the Novelty Problem. Josh Armstrong emends Lewis’ account to solve the Novelty Problem. I argue that Armstrong's emendation fails and that neither he nor Lewis has an adequate response to the Agreement Problem.