Hi, Recently I had a problem with adding a new tag (e.g. "foobar foo.bar."). This tag simply cannot be added to a RackTables up to 0.20.1: define ('TAGNAME_REGEXP', '/^[\p{L}0-9]([. _~-]?[\p{L}0-9])*$/u'); ... if (!validTagName ($sic[$argname])) throw new InvalidRequestArgException ($argname, $sic[$argname], 'Invalid tag name'); Unfortunately there is no documentation for this code. Maybe anyone know more about this behavior?