It seems Facebook’s CEO is fed up with some of his employees’ disregard for the Black Lives Matter movement.

Gizmodo reports that Mark Zuckerberg posted a memo on a company announcement page expressing his disappointment in people who have crossed out “Black Lives Matter” and written in “All Lives Matter” on the Menlo Park headquarters’ “signature wall.”

“Despite my clear communication at Q&A last week that this was unacceptable, and messages from several other leaders from across the company, this has happened again. I was already very disappointed by this disrespectful behavior before, but after my communication I now consider this malicious as well,” he wrote. “There are specific issues affecting the Black community in the United States, coming from a history of oppression and racism. ‘Black lives matter’ doesn’t mean other lives don’t—it’s simply asking that the Black community also achieves the justice they deserve.”

He also said that the company is working to identify the offenders, and he encouraged employees to attend a March 4 Black @ Town Hall to “educate themselves about what the Black Lives Matter movement is about.” Per data released last June Facebook’s staff is just 2 percent Black.

The screenshot of the full post is below, courtesy of Gizmodo.