The present invention concerns a method for the selection of a virus comprising the steps of: (a) providing a virus encoding and displaying a fusion polypeptide, said fusion polypeptide comprising a heterologous polypeptide inserted into the sequence of a viral coat protein polypeptide, wherein said virus comprises a cleavable site located within a displayed polypeptide; (b) exposing the virus to a cleaving agent; (c) propagating the virus comprising intact fusion protein.