Setting ZERO as Discounted Member Price

For some reason, I cannot set the discounted member price to zero. When I attempt to save the match with the “Allow Discounted Price for …” box CHECKED and the value for the price set to 0, it ends up UNCHECKING the box. If I put a non-zero amount in for the price, it saves and works perfectly. How do I set a discounted price of zero?

Please advise & thanks for your help!