Amazon’s anti-union efforts have been dealt a major blow, with the company losing a bid to overturn a vote by its employees to unionize.

Workers at the Staten Island, N.Y voted to unionize and join the Amazon Labor Union (ALU), but Amazon filed an appeal, requesting the vote be re-taken. According to NPR, a federal labor official with the National Labor Relations Board (NLRB) has rejected Amazon’s appeal in its entirety, ruling that the union should be certified.

ALU president Chris Smalls celebrated the news in a tweet:

The NLRB ruling is a significant setback for Amazon, a company that is notoriously anti-union. The company has aggressively pushed back against union efforts, even to the point of making its own investors uncomfortable. Amazon has also hired Pinkerton detectives to monitor organizing efforts on the part of its employees.

With the Staten Island precedent, Amazon will likely face much wider unionization efforts.