Few existing approaches towards architectural evolution deal with unanticipated evolution. This is an important restriction, since a lot of architectural changes are very di cult to anticipate. The reuse contract formalism has been designed speci cally to deal with unanticipated software evolution, and has already proven its practical use in di erent domains. We claim that the reuse contract approach can be applied to the domain of software architectures, to manage unanticipated evolution of software architectures.