(not a bug, just bad eyes) WAR BUG - Independence War 'Lordship of Gower'

[Nootie the Cutie]

I am the Kingdom of England. They have reach War Exhaustion. I won. Their single county is occupied and they are the War Leader. I can't annex the land for some reason. It simply says over it 'Invalid Target' without explanation.

Surely this is a bug. Even if France is helping them, they are not the War Leader.
I am not one to complain. But victory is victory.

Edit: So after the tick over into the next month. I checked the War Tab. A new bar saying 'Reign Subject In' was added. This addressed the 'problem' I thought I had