Dean Thomas Morton, Jr., appeals following his guilty plea to possession with intent to distribute less than 100 grams of a mixture containing a detectible amount of phencyclidine. The Government has waived Morton’s appeal waiver in the plea agreement by not seeking to enforce it. See United States v. Story, 439 F.3d 226, 230 (5th Cir. 2006).

Morton argues that his sentence is invalid in light of United States v. Booker, 543 U.S. 220, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005), because the district court applied the Sentencing Guidelines as if they were mandatory. We review for plain error. See United States v. Valenzuela-Quevedo, 407 F.3d 728, 732 (5th Cir.), cert. denied, — U.S. -, 126 S.Ct. 267, 163 L.Ed.2d 240 (2005). To prevail under a plain-error analysis, Morton must show, among other things, that the error prejudiced him by adversely affecting his substantial rights. See id. at 733.

Morton fails to identify anything in the record to suggest that his sentence would have been lower had the court applied the Sentencing Guidelines as advisory rather than mandatory. See id. He thus fails to establish prejudice to his substantial *448 rights. See id. The judgment of the district court is AFFIRMED.