Robert Mueller has requested that his longtime aide Aaron Zebley appear as a witness during his highly anticipated testimony in front of the House Judiciary Committee on Wednesday, The New York Times reports. Zebley, who was Mueller’s chief of staff at the FBI, reportedly coordinated the former special counsel’s Russia investigation team and served as a conduit with the Justice Department. “Aaron Zebley was the Deputy Special Counsel and had day-to-day oversight of the investigations conducted by the Office,” a spokesperson for Mueller said on Tuesday. “He will accompany Special Counsel Mueller to the Wednesday hearings, as was discussed with the committees more than a week ago.”

If Zebley takes the oath to testify, House rules could disqualify him from privately conferring with Mueller during the hearing—a role he would otherwise likely take. Democrats on the Judiciary Committee have yet to agree to the request. According to a committee spokesman, Mueller is currently the only witness listed for the hearing.