Missouri Tax Overrides for Vertex March 2018 Update

Hello, I've  tested the new Missouri standard deduction amounts using the March 2018 Vertex. It appears to be working correctly with the exception of exempt employees. In the past, we've record 99 on the tax override screen. However, Vertex seems to be bypassing the tax override screen now that Missouri no longer allows personal exemptions. How do we set up employees who's claimed exempt on their Missouri W4 now?