Constraint eyes doesn't work

Hi,

I’ve encountered an issue using the CC5 HD rig in Blender.

When moving the CTRL_C_eye manually everything works as intended.

But when I add a constraint to CTRL_C_eye it’s not affecting the eyes, although the rig moves to the desired location.

Somehow the eye bones are locked (?) for constraints because manual movement is possible.

Hopefully there is someone who can help me with this.

Thanks in advance.