Erick Clarke, a federal prisoner who pled guilty to unlawfully attempting to reenter the United States without consent in violation of 8 U.S.C. § 1326(a), appeals pro se the district court’s dismissal of his post-conviction motion to dismiss his indictment based on lack of jurisdiction. 1 Finding no error, we affirm.

More than a year after Clarke was sentenced for the foregoing offense, he moved to dismiss the underlying indictment on the grounds that it was jurisdictionally defective and had been constructively amended. The district court, finding that Clarke’s case was closed and that more than a year had passed since sentencing, determined it lacked jurisdiction to decide the motion and therefore dismissed it. 2 *970 On appeal, Clarke identifies no source of subject matter jurisdiction that would have empowered the district court to reach the merits of his motion. Clarke nevertheless contends that he is entitled to dismissal of the indictment because: (1) the indictment should have contained an allegation of willfulness; (2) Clarke was charged with and pleaded guilty to “attempted reentry,” but the written plea agreement and the judgment of conviction describe his offense as one of unlawful re-entry and do not use the term “attempt”; and (3) the attribution of this “[unjindicted offense” to Clarke violates Blakely v. Washington, 542 U.S. 296, 124 S.Ct. 2531, 159 L.Ed.2d 403 (2004) and United States v. Booker, 543 U.S. 220, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005).

A district court’s subject matter jurisdiction is subject to de novo review. See United States v. Perez, 956 F.2d 1098, 1101 (11th Cir. 1992) (per curiam). Clarke essentially claims that his indictment was so defective as to fail to invoke the district court’s jurisdiction or state an offense. Generally, a motion alleging a defect in an indictment must be raised before trial, “but at any time while the case is pending, the court may hear a claim that the indictment ... fails to invoke the court’s jurisdiction or to state an offense.” Fed. R.Crim. P. 12(b)(3)(B) (emphasis added). By the time Clarke moved to dismiss his indictment, he had already pled guilty and been sentenced — and the period to appeal the conviction and/or sentence had long since passed. See Fed. R.App. P. 4(b)(1). 3 Thus, Clarke’s case was not “pending” within the meaning of Rule 12(b)(3)(B) when he filed his motion to dismiss, and the district court correctly refused to entertain the motion. See United States v. Patton, 309 F.3d 1093, 1094 (8th Cir. 2002) (per curiam) (holding that district court properly denied Rule 12(b) motion where proceeding that led to prisoner’s conviction was no longer pending); United States v. Wolff, 241 F.3d 1055, 1056-57 (8th Cir. 2001) (per curiam) (“After final judgment was entered and Wolff did not file a direct appeal, the proceedings were no longer pending.”). Moreover, Clarke’s motion was effectively a collateral attack upon his sentence, and he may not circumvent habeas requirements by presenting his challenge under a different guise. Cf. Patton, 309 F.3d at 1094.

Upon review of the record, consideration of the parties’ briefs, and for the reasons stated above, we affirm the district court’s dismissal of Clarke’s post-conviction motion to dismiss the indictment.

AFFIRMED.