There is provided a method, apparatus and computer program product for causing a network repository function to perform: receiving, from a network function service consumer, an access request for an access authorization token, the request comprising a first identification of the network function service consumer and a first identification of at least one network slice on which access is requested; generating an access token in response to the request, the access token comprising at least one network slice identifier for the at least one network slice identified by the first identification; and providing the generated access token to the network function in response to the request for an access authorization token.