Maven pugin issue

Colleagues, may be someone met with the same issue and solved it somehow. Please advise.

I run SoupUI tests during Maven build and keep getting the error

Warning: validation was turned on but an org.xml.sax.ErrorHandler was not
set, which is probably not what is desired.  Parser will use a default
ErrorHandler to print the first 10 errors.  Please call
the 'setErrorHandler' method to fix this.
Error: URI=null Line=2: Document root element "soapenv:Envelope", must match DOCTYPE root "null".
Error: URI=null Line=2: Document is invalid: no grammar found.

I tried to use soapui-maven-plugin 4.6.1, soupui-pro-maven-plugin 5.1.2 and with both got the above error.

The test itself calls soap requests (webservices) and reads responses. When I run the test in SoapUI all go well.