A grand jury recently returned a third updated indictment against Minnesota businessman Robert Walker, who was recently arrested and accused by the FBI of tampering with a witness involved in his investment fraud case.

Walker, best known for inventing the Sleep Number Bed, pleaded not guilty to federal charges last year that stem from allegations that he and others defrauded investors in Bixby Energy Systems, Inc., a Ramsey-based startup that he founded after leaving Plymouth-based Select Comfort.

In August, a new criminal complaint was filed against Walker, and it reportedly accused him of tampering with a government witness in his case by sending false information by e-mail and raising money for Bixby despite his pending criminal case. Those acts allegedly violated conditions of Walker’s release pending his upcoming trial. Walker’s lawyer told the Star Tribune at the time that his client would contest every allegation in the complaint and fight “with full force.”

Now, a newly updated indictment from a grand jury, which was made public Wednesday, shows that Walker faces a total of 18 charges—including one count of witness tampering. The latest indictment accuses Walker of attempting to influence the testimony of a witness. According to a Star Tribune report, the witness is scheduled to testify against Walker at a trial set for next January.

Walker started Select Comfort in 1987 but sold his majority shares in 1991 to start his own alternative energy business, Bixby. Bixby focused on “coal gasification,” which was designed to convert coal into clean-burning natural gas, but Walker has been accused of misleading investors, among other things. Read more about the history of the Walker case here.