John Earl Thomas, in reliance on Blakely v. Washington, — U.S. -, 124 S.Ct. 2531, 159 L.Ed.2d 403 (2004), argues that the district court plainly erred in imposing a sentence based on facts not alleged in the indictment, not admitted by him in court, and not proved to a jury beyond a reasonable doubt. Thomas challenges on Blakely grounds the district court’s findings that he be held accountable for sentencing purposes for 612.6 grams of cocaine base and that he be held accountable for possession of a firearm.

To demonstrate plain error, Thomas has the burden of showing an error that is obvious and that affects his substantial rights. United States v. Mares, 402 F.3d 511, 520 (5th Cir. 2005), petition for cert. filed (Mar. 31, 2005) (No. 04-9517). To show that the error affected his substantial rights, Thomas has the burden of demonstrating that “the sentencing judge — sentencing under an advisory scheme rather than a mandatory one — would have reached a significantly different result.” Id. at 521 (citation omitted). Thomas has not shown that the district court would have imposed a different sentence. Accordingly, we AFFIRM the judgment of the district court.