You're unlikely to get it reversed. Get a carve-out agreed. You should be able to reasonably work that out by indicating you're working on X, in your own time

You're unlikely to get it reversed. Get a carve-out agreed. You should be able to reasonably work that out by indicating you're working on X, in your own time, on your own equipment. X belongs to you and not the company. X is not in competition with the company. Most places will grant that with little fuss.