Let F be a 2-factorization of the complete graph Kv admitting an automorphism group G acting primitively on the set of vertices. If F consists of Hamiltonian cycles, then F is the unique, up to isomorphisms, 2-factorization of Kpn admitting an automorphism group which acts 2-transitively on the vertex-set, see [A. Bonisoli, M. Buratti, G. Mazzuoccolo, Doubly transitive 2-factorizations, J. Combin. Designs 15 (2007) 120