How to avoid this Rigify Error: Incorrect armature for type 'arm'

I added 2 bones to the hand for the thumb. I suppose this is causing this error:
"Bone ‘upper_arm.L’: Input to rig type must be a chain of 3 bones. Incorrect armature for type ‘arm’ "

I imagine it’s just a matter of updating the armature settings before hitting Generate Rig, if so, where exactly is this done?

Thanks guys

DPC

I have the exact same problem here. Been struggling the whole day with this issue.