According to the linguistic doctrine of necessary truth, modal truths depend on analyticity. It is commonly accepted that if modal truths depend on analyticity, they depend on meaning. It’s also accepted that if modal truths depend on analyticity, they are conventional, since analyticity itself is conventional. I argue that these two ways of characterising the linguistic doctrine are incompatible, and conclude that if the theory is true, modal truths depend on meaning but fail to be conventional.