Amazon warehouse workers in multiple European countries are walking off the job today in protest of poor working conditions, according to a report from NBC News. The strike is designed to coincide with Amazon’s Prime Day, the made-up holiday the e-commerce company uses to juice sales.

Amazon workers primarily in German, Poland, and Spain are participating, with union representatives alleging Amazon has been working to freeze salaries, reduce medical leave pay rates, and strip other rights from its warehouse workforce.

“The message is clear — while the online giant gets rich, it is saving money on the health of its workers,” Stefanie Nutzenberger, a top official responsible for retail workers at German trade union Verdi, told NBC. Germany’s strike will last one day, although Amazon claims it will not impact its ability to process orders and maintain shipping commitments during Prime Day.

Meanwhile, workers at a San Fernando fulfillment facility outside Madrid are engaging in a three-day strike to gain a more favorable contract after the former collective agreement for the Comisiones Obreras (CCOO) union expired. Spanish workers are trying to avoid restrictions on time off and wage cuts, and the same group organized a two-day strike back in March. In Poland, warehouse workers have organized a work-to-rule protest, which involves doing only the bare minimum required by contract as a way to slow down industrial productivity.

“We believe Amazon’s Fulfillment Center jobs are excellent jobs providing a great place to learn skills to start and further develop a career,” Amazon said in a statement given to Reuters. The company also believes that only a small fraction of its 12,000-person workforce in Germany, the largest international retail market after the US, are participating in the strike.

Stories of warehouse working conditions around the globe have been well documented over the years, with many accounts of troubling work conditions, long hours, and restrictions on overtime pay, time off, and even bathroom breaks. According to British journalist James Bloodworth, who went undercover as an Amazon worker for his book Hired: Six Months Undercover in Low-Wage Britain, warehouse workers were peeing into bottles to avoid missing their targets.

A study released in April by worker rights platform Organise found that nearly three out of every four Amazon warehouse workers avoided using the restroom to meet quotas, while more than half of all surveyed workers reported mental health issues since taking the job. About 80 percent of participants said they would not apply for a job at Amazon again.

Amazon CEO Jeff Bezos became the richest man in modern history today, Bloomberg reported, when his net worth, much of it tied up in Amazon stock, surpassed $150 billion. That puts him ahead of Microsoft co-founder Bill Gates, whose net worth when adjusted for inflation hit a peak of around $149 billion at the height of the dotcom boom in 1999.