ROS topic tools mux not registering my output when I roslaunch the mux node

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Very strange error and I have a workaround by simply adding another topic, and then manually selecting it from the using the MuxSelect service. It is just a minor annoyance.

According to the package documentation (http://wiki.ros.org/topic_tools/mux), the arguments are as follows:

mux <outopic> <intopic1> [intopic2...] [standard ROS arguments]

launch file:

<?xml version="1.0"?>

<launch>
    <node pkg="topic_tools" type="mux" name="mux_cmd_vel" args="cmd_vel move_base/cmd_vel joy/cmd_vel mux:=mux_cmd_vel"/>
</launch>

rosnode info /mux_cmd_vel outputs:

--------------------------------------------------------------------------------
Node [/mux_cmd_vel]
Publications: 
 * /mux_cmd_vel/selected [std_msgs/String]
 * /rosout [rosgraph_msgs/Log]

Subscriptions: 
 * /clock [unknown type]
 * /joy/cmd_vel [unknown type]
 * /move_base/cmd_vel [unknown type]

Services: 
 * /cmd_vel_select
 * /mux_cmd_vel/add
 * /mux_cmd_vel/delete
 * /mux_cmd_vel/get_loggers
 * /mux_cmd_vel/list
 * /mux_cmd_vel/select
 * /mux_cmd_vel/set_logger_level


contacting node http://amr:42221/ ...
Pid: 20173
Connections:
 * topic: /rosout
    * to: /rosout
    * direction: outbound (52187 - 10.27.159.119:47390) [11]
    * transport: TCPROS

Problem here is cmd_vel is supposed to show up as an output topic but it does appear in Publications when I use "rosnode info", nor does it appear in "rostopic list".