A Mickey Mouse button with the Disney icon’s white gloved hand raised in a fist as a symbol of fighting oppression is pitting workers against managers at Disneyland as union negotiations continue over a new contract for more than a third of the 35,000 park employees.

Master Services Council, which represents 13,000 Disneyland employees from four unions, filed unfair labor practice charges on Tuesday, June 11 on behalf of more than 500 workers who were disciplined for wearing union buttons with Mickey’s raised fist.

The charges will be investigated by the National Labor Relations Board, according to Master Services.