All of the Democratic presidential candidates who have qualified for next week’s primary debate are threatening to boycott it in response to a labor dispute between a food service company and workers at Loyola Marymount University, which is hosting the event.

Members of Unite Here Local 11, a union representing food service employees at Loyola Marymount, in Los Angeles, are in negotiations with the university’s food service provider, Sodexo. The union said in a statement on Friday that it had been unable to reach an agreement.

“We had hoped that workers would have a contract with wages and affordable health insurance before the debate next week,” the statement said. “Instead, workers will be picketing when the candidates come to campus.”