A group of roughly 4,000 United Auto Workers union members rejected a tentative contract agreement with Mack Trucks Sunday, setting them up to go on strike starting Monday morning. It’s the second major strike undertaken by the union in recent months, after some 25,000 UAW members went on strike at Detroit’s “Big Three” auto manufacturers last month. The agreement rejected Sunday would have given workers at Mack Trucks a 20% increase in wages over the next five years—and no increases in health insurance premiums—though the proposal fell well short of what union members were asking for. “I’m inspired to see UAW members at Mack holding out for a better deal, and ready to stand up and walk off the job to win it,” UAW president Shawn Fain said Sunday in a statement.