How to set params to hokuyo_utm30lx in hector_models?

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I want to simulate Turtlebot2 with UTM-30LX on Gazebo. Not in real. So I changed Turtlebot2 model with kinect like tutorial.

The difference tutorial and mine is to set Topic name of UTM-30LX. According to hokuyo_utm30lx_model in hector_models, it can be defined Topic name with a parameter ros_topic. So I set the ros_topic a value like below. But error occured like below.

Could you tell me how to set ros_topic param?

My xacro code is below.

<?xml version="1.0"?>
<!--
    - Base      : kobuki
    - Stacks    : hexagons
    - 3d Sensor : kinect
-->    
<robot name="turtlebot" xmlns:xacro="http://ros.org/wiki/xacro">
  <xacro:include filename="$(find hector_sensors_description)/urdf/hokuyo_utm30lx.urdf.xacro"/>

  <xacro:include filename="$(find turtlebot_description)/urdf/turtlebot_common_library.urdf.xacro" />
  <xacro:include filename="$(find kobuki_description)/urdf/kobuki.urdf.xacro" />
  <xacro:include filename="$(find turtlebot_description)/urdf/stacks/hexagons.urdf.xacro"/>

<xacro:include filename="$(find turtlebot_description)/urdf/sensors/kinect.urdf.xacro"/>

  <kobuki/>
  <stack_hexagons parent="base_link"/>
  <sensor_kinect  parent="base_link"/>
  <hokuyo_utm30lx_model name="hokuyo_laser" parent="base_link">
    <origin xyz="0 0 +0.30" rpy="0 0 0" />
    <ros_topic>/scan</ros_topic>
  </hokuyo_utm30lx_model>
</robot>

Error Message is following.

Unused block "ros_topic"

XacroException(u'Unused block "ros_topic"',)
when instantiating macro: hokuyo_utm30lx_model (/home/yoshi/catkin_ws/src/hector_models/hector_sensors_description/urdf/hokuyo_utm30lx.urdf.xacro)
in file: /home/yoshi/catkin_ws/src/turtlebot/src/turtlebot/turtlebot_description/robots/kobuki_hexagons_kinect.urdf.xacro
Invalid <param> tag: Cannot load command parameter [robot_description]: command [/opt/ros/kinetic/lib/xacro/xacro --inorder '/home/yoshi/catkin_ws/src/turtlebot/src/turtlebot/turtlebot_description/robots/kobuki_hexagons_kinect.urdf.xacro'] returned with code [2]. 

Param xml is <param command="$(arg urdf_file)" name="robot_description"/>
The traceback for the exception was written to the log file

Environment
Ubuntu16.04, ROS Kinetic
hector_models: I use the version commited on Aug 25, 2017