If the rest of the house is exceptional, there might be a buyer who will overlook the problem, but it will almost always be a deal breaker. You are left with the option of having the estimate done and offering to have the problem fixed before title transfer, or doing it now.
If you have it repaired make all documentation and warranties available to the buyer. Ask the company doing the work if the buyer could contact them directly with questions. Before and after pictures can sometimes be helpful in cases like this.
Thanks, I hope things work out for you !! Feel free to contact me directly.