In June, UK staff at the nonprofit that runs Wikipedia became the first to announce their intention to form a union. Now, US-based employees at the Wikimedia Foundation are joining the union drive, but management at the nonprofit has declined to voluntarily recognize their union.

“While the Wikimedia Foundation touts to the public that they plan to take a neutral stance in our organizing efforts, they have already proven that not to be the case behind the scenes,” a press release sent by Communications Workers of America, with which Wiki Workers United is affiliated, reads in part. “When the Foundation rejected our request for voluntary recognition this week, they immediately sent out to employees and the public statements couched in classic union-busting rhetoric, rhetoric undoubtedly provided by outrageously expensive union-avoidance law firms. This insulting and wasteful use of Foundation resources is both an insult to Foundation employees and to the Free Knowledge Movement as a whole.”

In a public statement, the foundation said it believes a secret ballot election with the NLRB is the “appropriate path forward.”

The unionization efforts come at a time when tensions are high between the foundation and the thousands of unpaid volunteers who edit, write, and maintain Wikipedia. In May, hundreds of Wikipedia editors threatened to go on strike after the foundation dissolved an engineering team that worked closely with volunteers. Some volunteers questioned whether the layoffs were related to union efforts, which the foundation denied.