Switched from salary with overtime (non-exempt) to exempt with no pay change via /r/sysadmin

Is legal? I thought, all things being equal, an exempt employee was supposed to get paid more than an non-exempt employee, because there is the assumption that they will sometimes have to work more than 40 hours, so the increased base rate has assumed overtime "built-in".

I've been with the company for 3 years and they dropped this on me out of no where. My title is Junior System Administrator, but I was hired as a Level 2 HelpDesk Tech. I can understand overtime for a helpdesk tech since you can usually leave on time, but I was a Junior System Administrator with overtime for a whole year before this switch recently.