UK-based staff at the Wikimedia Foundation (WMF), the nonprofit that supports Wikipedia, are pushing forward with their unionization drive. On Wednesday, the staff sent a letter to WMF management requesting the organization voluntarily recognize the union.

“The WMF has undergone a period of significant change in recent months, escalating workers’ concerns over transparency, trust, and the organisation’s future direction,” a press release from the Communication Workers Union reads. “The workers are longtime contributors and organisers, and are deeply committed to the Wikimedia movement.”

WMF staff are based around the world, and the UK contingent is the first to seek union recognition. Workers have been organizing for months under the Wiki Workers United umbrella, and the UK has the second-highest number of WMF employees after the US, the press release says.

The letter sent on Wednesday comes after weeks of tense relations at WMF and Wikipedia. In May, the foundation announced it was disbanding a beloved team that worked closely with Wikipedia contributors, the army of editors, writers, and other volunteers who create and maintain the encyclopedia. (Contributors are not employees of WMF, though some have gone on to work for the foundation in a formal capacity.)

The announcement of potential layoffs came as a shock to many, and both volunteers and some former WMF employees expressed concern over the future of Wikipedia. Some questioned whether the move was related to WMF staff efforts to unionize their workplace. At the time, WMF chief of staff Nadee Gunasena denied that the disbanding (and potential layoffs) were related to union activities, and told The Verge that the organization “respect[s] the rights of all eligible staff to vote, and if the majority of eligible staff vote in favor of representation, we will proceed to negotiate in good faith.”

In response to the disbanding, volunteers rallied behind Wiki Workers United: More than 1,100 contributors have signed a petition saying they would be willing to participate in collective action if the union called for it. Collective action could mean volunteers might even go on strike, refusing to edit and maintain Wikipedia except for extreme cases.

The Wikimedia Foundation didn’t immediately respond to a request for comment. The UK-based group of Wiki Workers United did not respond in time for publication.