[Feed Validation Service] Error while checking URL with umlaut

While checking the feed of a german Wiki, i encountered the following error:
http://validator.w3.org/feed/check.cgi?url=http%3A%2F%2Fwww.vms-tutorial.de%2Fwiki%2FSpezial%3ALetzte_%25C3%2584nderungen
The original url: http://www.vms-tutorial.de/wiki/Spezial:Letzte_%C3%84nderungen
i think this comes only from the umlaut 'Ä', cause the check is successfull on another page without umlauts in url:
http://www.vms-tutorial.de/wiki/Spezial:Neue_Seiten
http://validator.w3.org/feed/check.cgi?url=http%3A%2F%2Fwww.vms-tutorial.de%2Fwiki%2FSpezial%3ANeue_Seiten

is it possible to fix this?

thanks.