Defendant Dominic Lieder was a member of a drug ring. He was arrested after he sold methamphetamine to an undercover law enforcement officer. Lieder provided substantial assistance to law enforcement both before and after pleading guilty to the offense of aiding and abetting in distribution of methamphetamine. At the sentencing hearing, the Government moved for a downward departure of Lieder’s sentence based on his substantial assistance. See United States Sentencing Guidelines § 5K1.1. Accordingly, the district court reduced Lieder’s sentence from the recommended guideline range of 108-135 months to 57 months.

Lieder now appeals his sentence, arguing that the district court abused its discretion in failing to depart downward more than 57 months. It is well-settled that a challenge to the sheer amount of a downward departure based on substantial assistance is not cognizable on appeal. See United States v. Williams, 324 F.3d 1049, 1050 (8th Cir. 2003); United States v. McCarthy, 97 F.3d 1562, 1576-77 (8th Cir. 1996). The only exception to this rule is when the district court refuses to depart *325 downward on the basis of bad faith or an unconstitutional motive. McCarthy, 97 F.3d at 1578. Since Lieder does not allege this exception, his appeal is summarily denied.

Accordingly, we deny the appeal for lack of jurisdiction.