BART's largest unions announced Tuesday that they will be filing a lawsuit against the transit agency's Board of Directors, according to a union representative.

The unions, Service Employees International Union Local 1021 and Amalgamated Transit Union Local 1555, said they are filing the lawsuit in response to the Board of Directors removing a medical leave provision when they approved the latest labor contract between workers and management.

The workers contend that the provision was in the contract all along and had been signed-off on as early as July. Management contends that the provision was put in the contract by mistake by an unnamed “temporary employee.” The board says they removed the provision because it would be too costly to the agency. The unions believe that the contract negotiated and signed by the unions and management, which the unions ratified, should stand as-is.

The unions will be holding a news conference at 11 a.m. this morning to further discuss the lawsuit.