gz joint and SDF file, "Unable to find joint[robot::knee]"

edit

See This: https://youtu.be/r2DEa_xAeV0

I have a SDF file: model.sdf
With the World file: set_joint.world
And the model plugin: set_joint.cc

I can control the joints from the model plugin but not directly with:

gz joint -m robot -j knee -f 1000

I get from gzserver (running verbose):

[Err] [JointController.cc:289] Unable to find joint[robot::knee]

However if i run
gz model -m robot -j knee -i
I get: model.msg
where i can see that :

joint {
  name: "robot::knee"
  id: 43
  angle: 0
  type: REVOLUTE
 ...

What am i missing?

UPDATE:
I have updated to Gazebo 7 and the joint moves with "gz joint -m robot -j knee -f 1000", but i still get the error "Unable to find joint[robot::knee].." strange that it manages to apply a force to a joint its unable to find ;)

I Uploaded files instead of linking to external source, used model.msg because .txt was not supported.