We compare the role of state invariants in Z and other state- based formalisms with that of abstract machine invariants in B.We argue a case for bringing B into line with the other formalisms in its use of in-472-489 variants, and show how this can be achieved by one small extension to B’s underlying semantics concerning the multiple composition operator, which has in any case already been proposed by others from different motivations. We illustrate the utility of our proposal with a small specification example, our Electronic Thesaurus.