Nillable header element is missing in soap header

SoapOutInterceptor moves nillable header element to soap body when its value is set to null[1]. For example, when the following header part value is set to null, this nillable element will appear in soap body.
<code>
public String echo(@WebParam(name = "message") String message.

@WebParam(name = "paramOut",mode = WebParam.Mode.INOUT, header = true) Holder<String> paramOut)

{ paramOut.value = null; return "echo: " + message; }

</code>
<soap:Body><ns2:echoResponse xmlns:ns2="urn:echo"><result>echo: test</result></ns2:echoResponse><ns2:paramOut xmlns:ns2="urn:echo" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/></soap:Body>