Bad news for Montreal transit maintenance workers.
They were supposed to starting job action on Saturday.
The labour tribunal has ruled the union's essential services were insufficient.
The workers planned on refusing overtime for a month as a pressure tactic.
The tribunal gave the union until midnight to agree to modify their list of essential services in accordance with its recommendations, but the union failed to do that by the deadline.
The workers been embroiled in a conflict with management over working conditions.