Lease Mistake - Omits 2-year Option - Divide County, ND

I found that my lease had omitted a 2 year option , I was not sure , this lease included some extraneous material about an option which seemed to be surface rights , so I called landman . yep , it had been forgotten, I wonder if they would have found it before the 45 day sight draft is paid to me., Anyway this was a moral obligation on my part to disclose this mistake , Norhwest Divide County ND.