Pedro Zarco Flores (“Flores”) appeals his guilty-plea conviction and sentence for possession of more than five kilograms of cocaine with intent to distribute, a violation of 21 U.S.C. § 841(a)(1) and (b)(1).

Flores contends that the district court clearly erred in denying him a “safety valve” departure under U.S.S.G. § 5C1.2. Although the basic outline of Flores’s story of how he obtained the truck that was used to deliver 5.58 kilograms of marijuana appears believable, his answers to some of the district court’s specific questions about this matter suggests that he was not being entirely forthcoming about his role in the offense. After reviewing the record, we conclude that the district court did not clearly err in determining that Flores’s testimony about his role in the offense was not fully credible or “truthful.” See U.S.S.G. § 501.2(a)(5) (Nov.2002); United States v. Ridgeway, 321 F.3d 512, 516 (5th Cir.2003).

For the first time on appeal, Flores maintains that the sentencing scheme of 21 U.S.C. § 841 is facially unconstitutional in light of Apprendi v. New Jersey, 530 U.S. 466, 490, 120 S.Ct. 2348, 147 L.Ed.2d 435 (2000). As Flores concedes, his argument is foreclosed by this court’s decision in United States v. Slaughter, 238 F.3d 580, 582 (5th Cir.2000). Flores raises the issue only to preserve it for possible further review.

The judgment of the district court is AFFIRMED.