SoapUI ignores encoding in xml, outline and raw tab

I am using SoapUI Pro 5.1.2.

My generell settings for encoding in SoapUI is -Dfile.encoding=UTF8 to have the same encoding as the server in our architecture.

Now I have a request without any extra definition for encoding. The response from the service is html and Content-Type: text/html;charset=ISO-8859-1.

In the html tab the umlauts are correct but in xml, outline and raw tab the umlauts are wrong, so that my xpath assertion fails.

Do you have any idea why xml, outline and raw ignores ISO-8859-1?