Deleting Gazebo model causes Python to freeze

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Indigo on Ubuntu 14.04 with Gazebo 7.3 and Python 2.7

Whenever I call the Gazebo model deletion service, Python freezes. No errors or special messages appear when the deletion code runs. This happens whether I wait for the service to become available or not. I checked that the model name is correct.

from gazebo_msgs.srv import DeleteModel # For deleting models from the environment

def del_model( modelName ): # FIXME: Freezes Python, DO NOT USE!
    """ Remove the model with 'modelName' from the Gazebo scene """
    # delete_model : gazebo_msgs/DeleteModel
    del_model_prox = rospy.ServiceProxy('gazebo/delete_model', DeleteModel) # Handle to model spawner
    # rospy.wait_for_service('gazebo/delete_model') # Wait for the model loader to be ready 
    # FREEZES EITHER WAY
    del_model_prox(modelName) # Remove from Gazebo

There is no feedback from ROS / Gazebo as to what is happening. Why does this happen?