President Trump took to Twitter railed against a last-minute decision to allow the longtime aide of former Special Counsel Robert Mueller to appear beside him in a hearing Wednesday. Democrats on the House Judiciary Committee agreed to Mueller’s request to have Aaron Zebley with him, hours before the highly anticipated hearing. “Just got back only to hear of a last minute change allowing a Never Trumper attorney to help Robert Mueller with his testimony before Congress tomorrow. What a disgrace to our system. Never heard of this before. VERY UNFAIR, SHOULD NOT BE ALLOWED. A rigged Witch Hunt!” the president wrote.

Democrats on the House Judiciary Committee initially rejected Mueller’s request for Zebley to testify as a witness next to him, but later agreed that he could sit beside him and advise him in his answers. The House Intelligence Committee also agreed to let Zebley be sworn in for its hearing later in the day, The Washington Post reports. Zebley served as Mueller’s chief of staff when Mueller was FBI director, and he had a similar role inside the Special Counsel’s Office.