className REST parameter should be taken into account in REST implementation

The documentation says:

If className is specified, the result will also contain the data for the first object of the corresponding class.

However when I use the following I don't get any object properties for XWiki.XWikiUsers:

http://<server>/xwiki/rest/wikis/query?q=object:XWiki.XWikiUsers&wikis=xwiki&className=XWiki.XWikiUsers