nxt_rviz_plugin with Rosjava

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Hi!
I'm using the nxt_lejos_proxy package and rviz.
I would like to use the nxt_rviz_plugin, which displays data from a nxt_msgs::Range message as a cone. I've set the topic to /ultrasonic_sensor, but when i run the simulation I got:

Status:Warning
   Topic No messages received

Using rostopic echo /ultrasonic_sensor I can see that the ranges detected by the ultrasonic sensor are published on the /ultrasonic_sensor topic. But looking in the class ROSProxy.java I've seen that the message published on that topic is a sensor_msgs/Range and not a nxt_msgs/Range.
Could this be the cause of the problem?And how can i solve it?