Sen. Bernie Sanders and employee activists have been thorns in Amazon’s side over the past year as they repeatedly call out the company on climate change and other issues. Now the Amazon antagonists are joining forces.

Sanders featured two of the most high-profile Amazon employee activists in a new campaign video circulating on social media. In it, Amazon UX designers Emily Cunningham and Maren Costa discuss their fight to pressure their employer into taking bolder climate action — and what it’s cost them.

“Amazon has tried to silence us,” Costa said. Amazon warned Costa and another employee that they could be fired for violating the company’s external communications policy. “They’ve threatened us with being fired if we continue to speak up.”

Amazon's workers are speaking out to say: Jeff Bezos should not be in the business of fossil fuel extraction. The company’s response? Retaliate with threats of firing. I stand with these employees who are fighting to protect the only home we have. pic.twitter.com/bvgsEH7nHj — Bernie Sanders (@SenSanders) January 6, 2020

In the video, Cunningham reflects on her experience at the company’s annual meeting last year. She presented a shareholder resolution urging Amazon to end contracts with fossil fuel companies and pursue other environmental goals.

“I was really scared standing up to my boss,” she said, but added, “I really felt like it was my moral responsibility given how urgent the climate crisis is.”

An Amazon spokesperson said the company’s external communications policy is “not new and we believe is similar to other large companies,” noting that the company began updating the policy in spring of 2019.

“We recently updated the policy and related approval process to make it easier for employees to participate in external activities such as speeches, media interviews, and use of the company’s logo,” the spokesperson added. “As with any company policy, employees may receive a notification from our HR team if we learn of an instance where a policy is not being followed.”

The shareholder resolution organized by Cunningham and other employee activists was voted down. Amazon did introduce The Climate Pledge in September, a commitment to meet the goals established in the Paris Agreement 10 years early. The company unveiled its carbon footprint for the first time as part of that announcement.

Employees like Cunningham and Costa, as well as Sanders and other presidential hopefuls, say the pledge does not go far enough. They are calling on Amazon to end partnerships with the oil industry and reduce its environmental impact more swiftly and aggressively.

“What corporate America knows, what many of us know, is the time is now to transform our energy system away from fossil fuel to energy efficiency and sustainable energy,” Sanders said in the video. “What we need is a strong grassroots movement protesting and saying that the future of this country is with other sustainable technologies.”