Custom properties and Library overrides

Hi there,
First, I’d like to say that I’m pretty new to blender. I’ve been investigating it for a few months now but I’m still far from understanding it all.
That said, I’m running into a problem and I can’t seem to find any solution :
I have my character rig in one scene, with custom properties on the armature (I use them to drive some constraints on the legs as an IK/FK switch). I made sure that I checked the “is Library Overridable” box on each of them.
However when I link my rig to a new scene and create a library override, my custom properties appear in grey, the tooltip telling me that I “can’t edit this property from an override data-block”
I guess I must be doing something wrong when linking my rig but I can’t quite figure it out
Any help would be much appreciated! :slight_smile: