spawn_model initial positions are temporary

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I'm launching my robot with:

<node name="lander_model" pkg="gazebo_ros" type="spawn_model" output="screen"
args="-urdf -param robot_description -model lander -J j_shou_yaw -1.5708
-J j_shou_pitch 1.5708 -J j_prox_pitch -2.7 -J j_dist_pitch 3" />

The model starts with joints set to the initial positions I specified with -J, but they immediately spring back to their origin poses as described in my URDF. Each of my joints is wired up with an effort_controllers/JointPositionController. Is there a way to get these joints to hold the specified initial positions? I don't want them to move until I command their controllers.