The U.S. judge overseeing Special Counsel Robert Mueller’s criminal case against Russians accused of interfering in the 2016 election agreed to appoint an independent lawyer to review pretrial evidence for possible national security issues before giving it to a Kremlin-linked defendant.

U.S. District Judge Dabney Friedrich in Washington on Monday approved a request to appoint a so-called firewall counsel envisioned as part of an earlier ruling on Mueller’s concern about providing evidence to Yevgeny Prigozhin, a longtime associate of Russian President Vladimir Putin. Prigozhin’s firm, Concord Management and Consulting LLC, was also indicted.

Mueller’s team had argued that if Prigozhin gains access to “sensitive” evidence, he could use it to thwart U.S. efforts to “prevent his continuing criminal activity in Russia and elsewhere” outside the U.S. Prigozhin, who provides food services to the Kremlin, is known as Putin’s chef. He and his company are among three firms and 13 people accused of producing propaganda at a Russian troll factory to whip up political strife in the U.S.

The U.S. said last month that the sensitive material includes information describing the government’s investigative techniques, identities of people and companies that are cooperating, and personal identifying information on individuals in the U.S. who were victims of identity theft.

Katherine Seikaly, a lawyer with Reed Smith who represents Concord, didn’t immediately return a call for comment.