delivered the opinion of the court:
The primary issue in this case is whether the 15-year sentencing enhancement for armed robbery while in possession of a firearm (720 ILCS 5/18 — 2(a)(2), (b) (West 2000)) is valid and enforceable. We hold that it is not.
BACKGROUND
Defendant, Saul Garcia, was charged with several offenses, including armed robbery while in possession of a firearm (720 ILCS 5/18 — 2(a)(2) (West 2000)). Although armed robbery is classified generally as a Class X felony, subsection (b) of the armed robbery statute provides that, for armed robberies while in possession of a firearm, “15 years shall be added to the term of imprisonment imposed by the court.” 720 ILCS 5/18 — 2(b) (West 2000). Prior to trial, defendant filed a motion arguing that the 15-year sentencing enhancement violates the proportionate penalties clause of the Illinois Constitution (Ill. Const. 1970, art. I, § 11). The circuit court of Kane County agreed with defendant’s argument and invalidated the 15-year enhancement. The State immediately appealed under Supreme Court Rule 604(a)(1) (145 Ill. 2d R. 604(a)(1)), construing the trial court’s order as an effective dismissal of the portion of the indictment charging defendant with armed robbery while in possession of a firearm. Because the trial court’s ruling invalidates a statute of this state, the appeal was taken directly to this court. 134 Ill. 2d R. 603.
ANALYSIS
A statute is presumed constitutional, and the party challenging the statute bears the burden of demonstrating its invalidity. In re K.C., 186 Ill. 2d 542, 550 (1999). This court has a duty to construe a statute in a manner that upholds its validity and constitutionality if it reasonably can be done. People v. Malchow, 193 Ill. 2d 413, 418 (2000). Whether a statute is constitutional is a question of law that we review de novo. Malchow, 193 Ill. 2d at 418.
This appeal is controlled by our decision People v. Walden, 199 Ill. 2d 392 (2002). In Walden, this court concluded that the 15-year sentencing enhancement for armed robbery while in possession of a firearm violates the proportionate penalties clause of the Illinois Constitution and therefore is unenforceable. Walden, 199 Ill. 2d at 397. Given the identity of issue between this appeal and Walden, we hold that the trial court’s order invalidating the 15-year enhancement in this case was proper.
By way of a cross-appeal, defendant seeks dismissal of the charges against him on the grounds that the delay occasioned by this appeal has denied him his rights under the speedy-trial provisions of the Code of Criminal Procedure of 1963 (725 ILCS 5/103 — 5 (West 2000)). In making this argument, defendant overlooks Supreme Court Rule 604(a)(4), which provides:
“The time during which an appeal by the State is pending is not counted for the purpose of determining whether an accused is entitled to discharge under section 103 — 5 of the Code of Criminal Procedure of 1963.” (Emphasis added.) 145 Ill. 2d R. 604(a)(4).
We therefore conclude that defendant’s speedy-trial argument is whoHy without merit.
CONCLUSION
The judgment of the circuit court of Kane County is affirmed, and the cause is remanded for further proceedings consistent with this opinion.
Affirmed and remanded.