The U.S. Court of Appeals for the Second Circuit has upheld the conviction of Mehmet Hakan Atilla, the former deputy general manager of Halkbank who served a 36-month prison sentence for his role in helping Iran to avoid billions of dollars in U.S. economic sanctions.

A three-judge panel of the Manhattan-based appeals court on Monday found a flaw in one of prosecutors’ main theories of liability in the case, but nonetheless upheld Atilla’s conviction, finding that the evidence against him was “overwhelming.”