If you really want to protect it, find a can of Scotchguard - they stopped selling it because of Freon or some other such propellant therein, but I saw new cans on the shelf in the last couple of weeks (at Home Depot of all places), so I guess they've found a suitable replacement! The stuff works, and it's designed for wool (and home application).

BUT as with any fabric (and the instructions for any similar product), start on a hidden spot - perhaps the under apron - to see if it's gonna do anything to the garment. Never had an issue with Scotchguard, but it never hurts to be safe!