UsedSpace still uses the old "Wiki Manager" plugin and doesn't work when the name of the main wiki database is not "xwiki"

Settings:

• XWiki Enterprise 6.4
• xwiki.db=manager
• xwiki.db.prefix=xwiki_

In "UsedSpaces" there is this code

#if($services.wikimanager)
    #set($dbs = $services.wikimanager.getAllWikis())
 #else
    #set($dbs = ["$xcontext.getDatabase()"])
 #end

which uses the old Wiki Manager plugin. Instead we should use new "$services.wiki".

However, even when I tried writing

#if($services.wiki)
  #set($dbs = $services.wiki.getAllIds())
#else
  #set($dbs = ${xcontext.database})
#end

I got that the name of the database is "xwiki", whereas it is "xwiki_manager".