John Johnson appeals his sentence of 40 months’ imprisonment following his conviction for being a felon in possession of a firearm, see 18 U.S.C. § 922(g)(1). He asserts that because the United States Sentencing Guidelines are unconstitutional, the district court 1 erred in giving them effect in sentencing him. It is true that in United States v. Booker, — U.S. -, -, 125 S.Ct. 738, 756, 160 L.Ed.2d 621 (2005), the Supreme Court held that, with exceptions not relevant here, it was a violation of the sixth amendment to enhance a guideline sentence on the basis of facts not found by a jury. But in this case no enhancements were applied, so the basic Booker holding is of no avail to Mr. Johnson.

We recognize that the district court nevertheless erred in passing sentence because it treated the guidelines as mandato *545 ry rather than advisory, see Booker, 125 S.Ct. at 756-57. But Mr. Johnson raised no objection to his sentence below, so we can review it for plain error only. We have examined the transcript of the sentencing hearing carefully and have discerned nothing in it that would indicate a reasonable probability that the sentence would have been shorter had the district court been aware that the guidelines were merely advisory. Mr. Johnson is thus not entitled to plain error relief. See United States v. Pirani, 406 F.3d 543, 552 (8th Cir. 2005) (en banc), cert. denied, — U.S. -, 126 S.Ct. 266, 163 L.Ed.2d 239 (2005).

Affirmed.