Affirmed in part, vacated in part, and remanded by unpublished PER CURIAM opinion.

Unpublished opinions are not binding precedent in this circuit.

Ezekiel Elijah Williams was sentenced to thirty-seven months of imprisonment for a Grade B violation of his supervised release. We vacate the district court’s sentence and remand for resentencing.

We conclude that the district court did not err in declining to recalculate Williams’s criminal history category in determining his sentencing range. See U.S. Sentencing Guidelines Manual, § 7B1.4(a) n.*, p.s. (revocation table) (“The criminal history category is the category applicable at the time the defendant originally was sentenced to a term of supervision.”). Any challenge to the original calculation of that category would be untimely. See United States v. Johnson, 138 F.3d 115, 117-18 (4th Cir. 1998).

But, as the parties both agree, the sentencing range itself was miscalculated. A Category IV offender who commits a Grade B violation, as Williams did, is subject to a range of twelve to eighteen months’ imprisonment. USSG § 7B 1.4(a), p.s. Because sentencing under the wrong Guidelines range constitutes reversible error, even under a “plainly unreasonable” standard, we are constrained to vacate the sentence and remand for resentencing. See United States v. Crudup, 461 F.3d 433, 439-40 (4th Cir. 2006) (providing standard of review).

Accordingly, although we affirm the revocation of supervised release, we vacate Williams’s sentence and remand for resen-tencing under the properly calculated Guidelines range. Because the facts and legal contentions are adequately presented in the materials before the court and argument would not aid the decisional process, we deny Williams’s motion for oral argument.

AFFIRMED IN PART, VACATED IN PART, AND REMANDED.