"unkrautbürste.de" blocked by "IDN Homographischer Angriffs-Schutz"

Hi,

why is the domain "unkrautbürste.de" blocked by "IDN Homographischer Angriffs-Schutz". If I disable that security feature, I can resolve the name again. The domain is a valid domain with a special German character in the domain name ("ü") and should not be blocked?

Thanks,

Michael