The Starbucks Workers United union has announced that thousands of employees at hundreds of locations nationwide will walk off the job on the coffee chain’s Red Cup Day promotional event this week. 

According to Reuters, employees cite staffing and scheduling issues as two main reasons for starting their “Red Cup Rebellion” this week. 

Red Cup Day – which falls on Thursday – is one of Starbucks’ most popular promotions. The company gives out free reusable cups, creating what a barista calls “one of the most infamously hard, understaffed days” of the whole year. 

“This year, on the heels of victories won by striking workers across different industries nationwide, Starbucks workers are taking the rebellion to the next level,” the union said. 

Staff shortages aren’t the only reason baristas are protesting; in June, workers at a Starbucks in Cypress Park walked off the job in protest of the removal of pride month decorations in addition to stalled contract negotiations. 

Workers United represents more than 360 stores and 9,000 unionized employees across America.