(CNN) Special counsel Robert Mueller's deputy Aaron Zebley is expected to appear next to the special counsel as his counsel at Wednesday's hearings on the special counsel's report, according to a House Judiciary committee source.

Zebley will be there to advise Mueller, but the special counsel will be the only one answering the committee questions, the source said. Democrats on the House Judiciary Committee only plan to swear in Mueller as a witness. However, Zebley will be sworn in to testify in front of the House Intelligence Committee, a committee aide told CNN.

Mueller made the last-minute request to have his deputy sworn in for Wednesday's blockbuster hearings before the Judiciary and Intelligence Committees on the Mueller report, in case he needed to help with any questions the special counsel could not fully answer himself, according to a source familiar with the matter.

"Aaron Zebley was the Deputy Special Counsel and had day-to-day oversight of the investigations conducted by the Office. He will accompany Special Counsel Mueller to the Wednesday hearings, as was discussed with the committees more than a week ago," said Mueller spokesman Jim Popkin.

Republicans on the House Judiciary committee immediately raised concerns that Democrats were making a major, last-minute change to the hearing to have Zebley to testify alongside the special counsel, less 24 hours before the hearings are scheduled to begin.

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