X’s firing of an employee who pushed back against a return-to-office policy imposed by Elon Musk last year was illegal, the National Labor Relations Board alleges. In what Bloomberg reports is the NLRB’s first formal complaint against X Corp., filed on Friday, the labor board accused the company of retaliating against software engineer Yao Yue for attempting to organize workers in the wake of the new policy. After Musk gave then-Twitter employees an ultimatum in November 2022 to return to the office, Yue urged others not to resign in response but instead “let him fire you.”

Musk at the time had told employees, “If you can physically make it to an office and you don’t show up, resignation accepted.” Yue was fired five days after tweeting about it and writing a similar post on Slack. In terminating her, the complaint filed by a San Francisco branch of the NLRB alleges the company violated federal labor law by “interfering with, restraining, and coercing employees” exercising protected rights, according to CNBC. A hearing is now set for January 30.

The formal NLRB complaint may be a first for X, but accusations of retaliation against employees are nothing new for a Musk-helmed company. In early 2023, Tesla workers in Buffalo, New York accused the company of firing them for unionizing, and eight SpaceX employees filed a complaint with the NLRB in 2022 claiming they were terminated for criticizing Musk.