CXF ClientProxy getClient “not a proxy instance”

I'm attempting to use WS-security with my Apache CXF client. I need to get a hold of the client endpoint so I can add a WSS4J interceptor. However, when I call ClientProxy.getClient() I get an IllegalArgumentException with the following message:

not a proxy instance

Code:

MailingService_ServiceLocator serviceLocator = new MailingService_ServiceLocator();
MailingService_PortType port = serviceLocator.getMailingServicePort();

Client client = ClientProxy.getClient(port);  // throws exception

...

// Create client interceptor
AuthenticationInterceptor authenticationInterceptor =
  new AuthenticationInterceptor(schemaNS, outprops, organizationName, null);

client.getEndpoint().getOutInterceptors().add(authenticationInterceptor);

Trace:

java.lang.IllegalArgumentException: not a proxy instance
    at java.lang.reflect.Proxy.getInvocationHandler(Unknown Source)
    at org.apache.cxf.frontend.ClientProxy.getClient(ClientProxy.java:93)

It turns out I was using the wrong code generation tool. I was using the org.codehaus.mojo axistools-maven-plugin, which gives you a service which extends java.rmi.Remote. However, I needed to use the org.apache.cxf cxf-codegen-plugin, which gives you a service that does implement Proxy.

New code:

MailingService_Service mss = new MailingService_Service();
MailingService service = mss.getMailingServicePort();

ClientImpl client = (ClientImpl) ClientProxy.getClient(service);

New pom:

<plugins>
  <plugin>
    <groupId>org.apache.cxf</groupId>
    <artifactId>cxf-codegen-plugin</artifactId>
    <version>2.6.0</version>
    <executions>
      <execution>
    <id>generate-sources</id>
    <phase>generate-sources</phase>
    <configuration>
      <sourceRoot>${project.build.directory}/generated/cxf</sourceRoot>
      <wsdlOptions>
        <wsdlOption>
              <wsdl>${basedir}/src/main/wsdl/myWsdl.wsdl</wsdl>
            </wsdlOption>
      </wsdlOptions>
        </configuration>
    <goals>
      <goal>wsdl2java</goal>
    </goals>
      </execution>
    </executions>
  </plugin>
</plugins>