Readonly method set-up with @Transactional don't work

class AlbumService {

   // No changes if false
   boolean transactional = true

   @Transactional(readOnly = true)
   def Object updateObject(album = null) {

       if(album){
           album.name = album.name + "Frakked"
           album
       } else {

           Album.list().each{
               it.name = "" + it.name + "Frakked"
               it
           }
       }
   }
}