Unsupported Content-Type: text/html; charset=UTF-8 Supported ones are: [text/xml]

After a webservice call we receive a web service response but we encounter the following error:

com.sun.xml.ws.server.UnsupportedMediaException: Unsupported Content-Type: text/plain; charset=utf-8 Supported ones are: [text/xml].

When making the same webservice call in SOAPUI it works fine.

What can cause this error?

Thanks!