Thousands of unionized Starbucks workers will walk off their jobs on Thursday, with the one-day work stoppages coming to protest the company’s stance with shops that voted to organize, according to Starbucks Workers United.

The labor action is timed to for Starbucks’ Red Cup Day, an annual event in which the coffee giant hands out holiday-themed reusable cups. Starbucks has refused to negotiate in good faith over staffing and other issues that are particularly acute during promotions, according to the union.

“Starbucks is creating unnecessarily stressful working conditions by scheduling promotion after promotion without increasing staffing,” Neha Cremin, a Starbucks worker in Oklahoma City, said in a statement to CBS MoneyWatch. “Starbucks has made it clear that they won’t listen to workers, so we’re advocating for ourselves by going on strike.”