The chief executive of Twitter had his account briefly suspended because of what he said was an “internal mistake.”

Jack Dorsey, who co-founded the social network in 2006, was locked out of his account, which had 3.9 million followers, for about 15 minutes on Tuesday night. During that time, anyone trying to access his account—with the handle @Jack—received an error message informing them that the account they were trying to view had been suspended.

Dorsey then tweeted saying “Just setting up my twttr…again (account suspension was an internal mistake),” a call-back to the first ever tweet, “just setting up my twttr,” which he sent on March 21, 2006. His previous tweets have been recovered but his follow count now stands at 2.67 million.

Dorsey’s ban follows a Twitter crackdown on far-right accounts, including the white nationalist Richard Spencer, who recently led audience members in a Nazi-style salute during a conference. Spencer described Twitter’s decision to suspend his account as “corporate Stalinism.”

“They’re purging people on the basis of their views,” he said.