Software development is witnessing the increasing need of version management techniques for supporting the evolution of model-based artefacts. In this respect, metamodels can be considered one of the basic concepts of Model-Driven Engineering and are expected to evolve during their life-cycle. As a consequence, models conforming to changed metamodels have to be updated for preserving their well-formedness. This paper deals with the co-adaptation problems by proposing higher-order model transformations which take a difference model recording the metamodel evolution and produce a model transformation able to co-evolve the involved models.