Calling service bus http proxy with basic authorization from pipeline

Hello,

On my service bus 12c I have a proxy service secured by Basic authorization. Authorization works when I pass it as http header from any external software like Postman. But when I try to send the same header from another pipeline as HTTP user header I get an error: General runtime error: com.bea.wli.sb.security.AccessNotAllowedException. How Can I pass the authorization credentials from a service bus pipeline to a proxy service so the authorization would work? No OWSM policy is added to that proxy.

Regards,

Tomasz