Professor doesn't tell TAs what should be on exams until the day of the exam

As a TA I am responsible for preparing problems and solution sets for the exams. Last time we had an exam, the professor didn't tell us which problems he wanted to select for the exam until the morning of the exam, which meant I had to write solutions for a large number of problems the night before the exam, most of which did not end up being on the exam. Now there is another exam coming up and I fear I will have to do this again. What should I do?