Running Manifold with 5 bolts

The farthest back stud on the driver's side of my engine was already snapped off when I took the manifold off. The previous builder just bolted it up with 5 bolts. Is this alright and just more prone to leaking or will it cause lasting damage like a cracked manifold or something? If I really need to do it, how do you fix it? I know that goes to a water passage so drain the coolant first? It's snapped off pretty flush with the head so it's not going to be a fun job, especially being the worst one to snap pretty much, but I guess if it's got to be done then I'll get it done.