Julian Castaneda appeals the sentence the district court imposed after Castaneda was convicted of drug charges. Citing United States v. Booker, — U.S. -, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005), Castaneda argues for the first time the district court committed error in sentencing him under a mandatory Guidelines scheme. We conclude the Booker error is plain, and given the court’s comments at sentencing while choosing a sentence at the bottom of the Guidelines range, Castaneda has shown a reasonable probability he would have received a lesser sentence under advisory Guidelines. See United States v. Pirani, 406 F.3d 543, 550-53 (8th Cir. 2005) (en banc), petition for cert. filed, *738 (U.S. July 27, 2005) (No. 05-5547). Accordingly, we remand for resentencing.