Gazebo 4 Contact sensor issue using URDF

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I am having an issue after I upgraded to Gazebo4 from Gazebo2. My reason to upgrade was to have the ability to use multiple contact sensor which apparently is only available 4.1 and higher. I am using URDF instead of SDF since I do plan on using the description for Rviz as well.

My environment is: Ubuntu 14.04; Gazebo 4, Ros Indigo. I am using the "libgazeborosbumper.so" plugin.

Here is my code:

<gazebo reference="left_bump_link">
<sensor type="contact" name="lside_bump_link">
  <always_on>true</always_on>
  <update_rate>10</update_rate>
  <contact>
    <collision>left_bump_link_collision</collision>
  </contact>
  <plugin name="lside_bumper_plugin" filename="libgazebo_ros_bumper.so">
    <bumperTopicName>lside_bumper</bumperTopicName>
    <frameName>lside_bump_link</frameName>
  </plugin>       
</sensor>
</gazebo>

The links and the joints work just fine and like I said, this code worked perfectly fine in Gazebo 2.

When I echo the rostopic "lside_bumper", it shows that it never makes a contact. When I did this on Gazebo2 it gave me all the values when the contact was made.

Has anybody experienced anything similar or anything obvious I am missing?