JobDSL Folder Creation Destroys Credentials

When using job-dsl-plugin to create a folder 

folder(my_folder) { 

  displayname("my_folder_name")

}

If the folder exists with Credentials attached to it, they are lost on recreation  . Is there anyway to wrap this in a conditional? if!(folder(my_folder) {blah..blah....}.  I believe the desired behaviour here is to not blow away the credentials attached at the folder level.