Ronnie Merrill challenges the sentence he received following his guilty-plea conviction for distributing less than 100 grams of heroin and less than 50 grams of crack cocaine, in violation of 21 U.S.C. § 841(a)(1). He first argues that the waiver-of-appeal provision in his plea agreement is unenforceable. Because the record reveals that the district court did not specifically advise Merrill that he had waived the right to appeal his sentence as part of his plea, Merrill is correct that the waiver-of-appeal provision in his plea agreement does not bar the instant appeal. See Fed.R.Crim.P. 11(b)(1)(N); United States v. Robinson, 187 F.3d 516, 518 (5th Cir. 1999).

Merrill next argues, for the first time on appeal, that the adjustments he received for being a career offender and for possessing a firearm under the Sentencing Guidelines violated his constitutional rights following United States v. Booker, — U.S. -, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005), and Blakely v. Washington, 542 U.S. 296, 124 S.Ct. 2531, 159 L.Ed.2d 403 (2004). The argument is reviewed for plain error. United States v. Mares, 402 F.3d 511 (5th Cir. 2005), petition for cert. *395 filed, — U.S. -, — S.Ct. -, — L.Ed.2d-, No. 04-9517 (U.S. Mar. 31, 2005).

In light of Booker, the district court erred in computing Merrill’s sentence based on judicially determined facts under a mandatory guidelines system, and that error was both plain and obvious. Mares, 402 F.3d 511, 520-521. Nevertheless, because Merrill has not demonstrated that the district court would have reached a different conclusion had it known that the Guidelines were advisory only, he has failed to demonstrate that the error affected his substantial rights. ** Id. at 520-521. Accordingly, Merrill has failed to carry his burden of demonstrating plain error, and the district court’s judgment is AFFIRMED.