Help! WSAS ignores "mustUnderstand" soap header parameter

In my SOAP11 request I specify mustUnderstand="0" as a parameter of the sequrity header.

<wsse:Security soapenv:mustUnderstand="0" xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">
...

In security header I have UserNameToken. Service that I want to call is not secured. As soon as mustUnderstand=0 (false) server should ignore security header. But all the time i got an error message:

org.apache.axis2.AxisFault: Must Understand check failed for header http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd : Securi>
      at org.apache.axis2.engine.AxisEngine.checkMustUnderstand(AxisEngine.java:102)
      at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:168)
      at org.apache.axis2.transport.http.HTTPTransportUtils.processHTTPPostRequest(HTTPTransportUtils.java:167)
      at org.apache.axis2.transport.http.AxisServlet.doPost(AxisServlet.java:142)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
      at org.eclipse.equinox.http.servlet.internal.ServletRegistration.handleRequest(ServletRegistration.java:90)
      at org.eclipse.equinox.http.servlet.internal.ProxyServlet.processAlias(ProxyServlet.java:111)
      at org.eclipse.equinox.http.servlet.internal.ProxyServlet.service(ProxyServlet.java:67)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
      at org.wso2.carbon.bridge.BridgeServlet.service(BridgeServlet.java:132)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
      at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
      at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
      at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870)
      at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
      at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
      at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
      at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
      at java.lang.Thread.run(Unknown Source)

Then we create a simple handler that removes all mustUnderstand flags where they are set to true:

package org.abi.axis.handler;

import org.apache.axis2.AxisFault;
import org.apache.axis2.context.MessageContext;
import org.apache.axiom.soap.SOAPBody;
import org.apache.axiom.soap.SOAPEnvelope;
import org.apache.axiom.soap.SOAPHeader;
import org.apache.axiom.soap.SOAPHeaderBlock;
import java.util.*;

public class RemoveMustUnderstandAll extends org.apache.axis2.handlers.AbstractHandler {

    public InvocationResponse invoke(MessageContext msgContext) throws AxisFault {
        //Setting mustUnderstand equal to true;
       	System.out.println("RemoveMustUnderstandAll: invoke "+msgContext);
        SOAPEnvelope env = msgContext.getEnvelope();
        SOAPHeader header = env.getHeader();
        if(header != null){
            for(Iterator itr = header.getChildElements(); itr.hasNext();){
                SOAPHeaderBlock headerBlock = (SOAPHeaderBlock) itr.next();
                if(headerBlock.getMustUnderstand()){
                	headerBlock.setMustUnderstand(false);
                	System.out.println("RemoveMustUnderstandAll ("+msgContext+"): setMustUnderstand(false) to "+headerBlock.getQName());
                }
            }
        }
        return InvocationResponse.CONTINUE;
    }
}

Registered it in the axis2.xml as a handler:

    <phaseOrder type="InFlow">
        .......
        <phase name="OperationInPhase">
            <handler name="RemoveMustUnderstandAll"
                     class="org.abi.axis.handler.RemoveMustUnderstandAll"/>
        </phase>
    </phaseOrder>

And in the log we can see that all mustUnderstand for the Security header equals to true... I think it's a bug of WSAS. Or maybe there is a special parameter???