Shields aren't part of calendrical dueling, so it definitely catches him - not precisely off-guard, but without a reflexive countermove, especially since he can't even strike the shield with sword. Build for killing in the presence of life-sustaining ship hulls or delicate calendrical devices, the sword only damages living tissue.

So he takes the blow on his forearm, a deep jarring that will bruise wonderfully, buying himself the time to skitter to back, jumping onto a chair and then the table, the better to bring down a high strike above and around the shield.