Amazon is once again ramping up its anti-unionization efforts, posting signs in its ALB1 warehouse in upstate New York, telling workers: “Don’t sign a card.”

Engadget was the first to break the story, with workers at the warehouse sending pictures of the signs to the outlet. According to one of Engadget’s sources, the digital signs cycle through seven slides, all of which discourage organizing.

“It’s on a constant loop while people punch in and punch out of their shifts,” he said, “[when] they go on their breaks, or they go on their lunch. Any time that we’re going to be up towards the front.”

Amazon has a long history of aggressively fighting unionization efforts, even breaking labor laws to do so. The company has been known to hire Pinkerton detectives to further its efforts and has even made investors uncomfortable with its aggressive tactics.

It remains to be seen if the National Labor Relations Board will challenge the legality of Amazon’s latest move.