Refactoring is an essential operation in software engineering, with the purpose of improving the structural qualities of software. An emerging trend in software engineering is the use of model-driven approaches in which models are used as first-class entities. The problem domain concepts used in models are formalised by a metamodel. Refactoring of metamodels is an important task in increasing the extensibility and maintainability of metamodels. However, changing the definition of a metamodel comes at the cost of introducing inconsistencies in modelling artefacts that are defined relatively to the metamodel. In this report, we present a framework extension for refactoring of metamodels that allows re-establishing consistency between the artefacts and the metamodel. We also discuss how refactoring patterns can be applied automatically on metamodels. The framework has been formally defined by a deductive system.