The United Auto Workers say General Motors canceled health insurance for more than 49,000 striking workers Monday night, without any notice.
The move means employees will need to sign up for COBRA insurance. COBRA is the federal insurance program for people who are out of work.
The union will have to dig into its strike fund more deeply than it apparently planned because of the decision.
Labor expert Harley Shaiken of UC-Berkley says in past strikes, companies have chosen to keep private insurance plans in place, and billed the union for them, in order to avoid disruption in coverage.
"GM's failed attempt to hurt our members and force us into a bad agreement was cold, heartless, and immoral," UAW spokesman Brian Rothenberg said in a press release.
GM says employees can enroll in COBRA by calling the GM Benefits and Service Center, and notes the benefits are retroactive to the beginning of the strike.