Oliver Schmidt, the former head of Volkswagen's U.S. regulatory compliance office during its emissions scandal, apparently has until Dec. 6 to decide if he is going to cooperate with federal prosecutors in their investigation.

The plea deal that Schmidt made with the U.S. Department of Justice on Aug. 4 said if Schmidt agrees to enter a cooperation agreement before his Dec. 6 sentencing date, nothing in the plea deal can supersede the new agreement.

The language in the plea deal suggests that so far Schmidt, who remains in custody while he awaits sentencing, has stayed mum about who worked with him to try and cheat Environmental Protection Agency emissions testing. He pleaded guilty Aug. 4 to two felonies—one count of conspiracy to defraud the United States, and one count of violating the Clean Air Act.