backup won't backup a certain virtual server because it has an alias domain name

hello can you please tell me a fix for the automatic backup issue “A new format backup can only be done when all virtual servers have a home directory”

this is because i use an alias for one of the servers…but it should be able to backup the home directory its not an alias meaning … i have a real home directory on server /home/ and then an alias domain to it … all i want to do is backup he main domain but whenever i select it i get this error

any advice?