Vacated and remanded by published opinion. Judge KING wrote the opinion, in which Judge DUNCAN concurred. Judge LUTTIG wrote a dissenting opinion.
KING, Circuit Judge:
Gay Sanford Washington appeals from the sentence imposed upon him in the Southern District of West Virginia after his plea of guilty to a single offense of felonious possession of a firearm, in contravention of 18 U.S.C. §§ 922(g)(1) and 924(a)(2). Washington contends that he was sentenced erroneously when the district court determined that his prior conviction for breaking and entering constituted a “crime of violence” under United States Sentencing Guidelines Manual §§ 2K2.1(a)(4) and 4B1.2(a)(2) (2003), and enhanced his sentence accordingly. As explained below, we vacate Washington’s sentence and remand for further proceedings consistent with United States v. Booker, — U.S. -, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005), and Shepard v. United States, — U.S.-, 125 S.Ct. 1254, 161 L.Ed.2d 205 (2005).
I.
On April 1, 2003, Washington entered a plea of guilty to being a felon in possession of a firearm. The applicable provision of [836]*836the Sentencing Guidelines, § 2K2.1(a), provides for a base offense level of 14, and for an enhanced base offense level of 20 when the defendant has been previously convicted of a “crime of violence.” USSG § 2K2.1(a)(4). In 1996, Washington was convicted in Putnam County, West Virginia, of the state law felony of breaking and entering. See W. Va.Code § 61-3-12. Washington’s initial Presentence Report (“PSR”) revealed that his prior conviction was for breaking and entering the offices of a drug and violent crime task force, and it characterized the offense as a “crime of violence.” The probation officer accordingly recommended that Washington’s offense level be fixed at the enhanced level of 20. Washington objected, asserting to the probation officer that his prior offense was not a “crime of violence” under the Guideline, or under our decision in United States v. Harrison, 58 F.3d 115 (4th Cir.1995) (concluding that defendant’s burglary of commercial building was not crime of violence). The probation officer accepted the objection and revised Washington’s PSR accordingly, lowering his base offense level to 14.
At Washington’s first sentencing hearing, on June 17, 2003, the Government objected to the PSR as revised. In objecting, the Government relied on § 4B1.2(a)(2) of the Guidelines, which provides that a “crime of violence” includes an offense which “is burglary of a dwelling ... or otherwise involves conduct that presents a serious potential risk of physical injury to another.”1 In support of this position, the Government contended that the circumstances of Washington’s prior offense, the breaking and entering of a drug and violent crime task force, “otherwise involve[d] conduct that presents a serious potential risk of physical injury to another,” USSG § 4B1.2(a)(2), bringing it within the Guideline definition.
In conducting the hearing, the sentencing court posed a series of pertinent questions to counsel on the crime of violence issue, including questions as to the specifics of Washington’s prior offense. It first inquired as to the title, function, and location of the Task Force whose offices were burglarized. In response, the Assistant United States Attorney represented to the court:
Your Honor, I believe ... that the building that was broken into housed this particular Drug and Violent Crime Task Force. In that particular building rests a great deal of potential for violence. Not only does it house evidence, narcotics, weapons, it frequently has — I believe this particular office has surveillance equipment, security alarms. It is frequently manned at all hours of the day and night, although I don’t believe it is routinely a 24-hour manned facility. I believe ... that an individual who breaks into such an office certainly creates this other type of potential for risk of violent injury....
(J.A. 61). The court inquired further as to the specifics of the offense, asking: “What else do you know about the circumstances of the break-in?” and “[y]ou don’t know the hour of the break-in or the day?” (J.A. 62). The court then continued the sentencing hearing to a later date, directing the parties to brief both the issue of what material the court could consider in [837]*837determining whether Washington’s prior offense was a “crime of violence,” and what specific conduct was at issue in the prior offense.2 The court also advised, “the government has the burden of proof on the matter.”
On June 19, 2003, the Government filed a sentencing memorandum setting forth a variety of allegations regarding Washington’s prior conviction. The memorandum advised that the crime was committed “[i]n the early morning hours of December 11, 1995,” when the “defendant along with two accomplices broke into the office of the Midwestern Task Force by breaking a ground-level window.” It also related, inter alia, that Washington and his “two accomplices” had stolen firearms and several varieties of drugs. The Government attached the police report and criminal investigation report to its memorandum.3
The factual background of Washington’s prior state conviction, as spelled out in the prosecution’s sentencing memorandum, was not contained in or suggested by the indictment itself, which merely alleged in Count 1 that Washington “did unlawfully and feloniously break and enter a building of the City of Hurricane ... occupied by the Midwestern Drug and Violent Crime Task Force with intent to ... steal” Task Force “goods and property.”4 Likewise, the plea materials of record in the state court proceeding provided no other details on the breaking and entering conviction.
At Washington’s final sentencing hearing on August 29, 2003, the court applied the “crime of violence” enhancement and sentenced accordingly. In so ruling, the court looked to the provisions of § 4B1.2(a)(2), specifying that a “crime of violence” includes a crime that “involves conduct that presents a serious potential risk of physical injury to another,” and to the accompanying Application Note. Because the break-in underlying Washington’s prior conviction was not of a dwelling, the court concluded that the earlier offense was not, in the abstract, a crime of violence. The court then made a two-tiered determination, characterized in the Statement of Reasons section of its Judgment Order as “findings of fact and conclusions of law” made by a “preponderance of the evidence.” (J.A. 165) (emphasis added). It ruled that the conduct “expressly charged” in the indictment warranted the conclusion that “breaking and entering of a government-owned building to steal the goods and property of a drug and violent crime task force is conduct that, by its nature, presents a serious potential risk of physical injury to another.” The court explained that conclusion as follows:
Based on common experience, it is reasonable to expect that quarters occupied by a drug and violent crime unit would [838]*838contain both drugs and guns that are protected from theft; that, even if no one affiliated with the task force was present at the time of a breaking and entering into its quarters, one or more members or employees of the task force may show up there at any time of day or night in view of the oft-times clandestine and nocturnal nature of their work; and such persons would be armed.
The act of breaking and entering such a facility is a reckless, dangerous act which, by its very nature, is fraught with serious potential for confrontation and risk of substantial physical harm to another.
(J.A. 166-67). Based on this assessment, the court fixed Washington’s base offense level at the enhanced level of 20, applied a three-level reduction for acceptance of responsibility, for a final offense level of 17, and sentenced Washington to thirty months of imprisonment.
II.
Washington has appealed his sentence, maintaining that the district court misapplied circuit precedent and the Guidelines in determining that his prior breaking and entering offense constituted a crime of violence. On appeal, he also contends that his sentence violated the Sixth Amendment, relying on Blakely v. Washington, — U.S.-, 124 S.Ct. 2531, 159 L.Ed.2d 403 (2004).
Because Washington did not raise his Blakely claim in the district court, we review that contention for plain error only. See Fed.R.Crim.P. 52(b) (“Plain errors or defects affecting substantial rights may be noticed although they were not brought to the attention of the district court.”). In order for Washington to prevail under Rule 52(b), “there must be an ‘error’ that is ‘plain’ and that ‘affect[s] substantial rights.’ ” United States v. Olano, 507 U.S. 725, 732, 113 S.Ct. 1770, 123 L.Ed.2d 508 (1993). Moreover, because “Rule 52(b) leaves the decision to correct the forfeited error within the sound discretion of the court of appeals,” we may exercise our discretion to recognize plain error only when “the error seriously affects the fairness, integrity or public reputation of judicial proceedings.” Id. (citation and internal quotation marks omitted).
III.
This appeal presents the question of the scope of the “fact of a prior conviction” exception to the Sixth Amendment protections outlined in Apprendi v. New Jersey, 530 U.S. 466, 120 S.Ct. 2348, 147 L.Ed.2d 435 (2000), and its progeny, including United States v. Booker, — U.S. -, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005). More specifically, it requires that we address the question of whether the Sixth Amendment is offended when a sentencing court makes findings of fact regarding the circumstances of a defendant’s prior conviction, and then relies on such findings to reach the conclusion that the prior conviction “otherwise involve[d] conduct that presents a serious potential risk of physical injury to another,” USSG § 4B1.2(a)(2), and enhances the defendant’s sentence as a result.
A.
Two important recent developments in Sixth Amendment jurisprudence guide our analysis of this case. First, in Booker, the Court held that the Sixth Amendment is contravened when a sentencing court, acting pursuant to the Guidelines, imposes a sentence greater than the maximum aur thorized by facts, other than the fact of a prior conviction, admitted by the defendant or found by the jury alone. Booker, 125 S.Ct. at 750-51. Second, in Shepard, the Court recently instructed that Sixth Amendment protections apply to “a disput[839]*839ed fact ... about a prior conviction.” 125 S.Ct. at 1262 (emphasis added).
1.
As the Court’s line of decisions originating with Apprendi make clear, the Sixth Amendment mandates that “any fact other than a prior conviction sufficient to raise the limit of the possible federal sentence must be found by a jury, in the absence of any waiver of rights by the defendant.” Shepard, 125 S.Ct. at 1262 (citing Jones v. United States, 526 U.S. 227, 243 n. 6, 119 S.Ct. 1215, 143 L.Ed.2d 311 (1999)) (emphasis added). This protection applies to the Sentencing Guidelines, which, though promulgated not by Congress itself but by the United States Sentencing Commission, had until recently the force and effect of law, and thus implicate the Sixth Amendment. Booker, 125 S.Ct. at 750. In order to determine whether a Sixth Amendment error occurred in Washington’s sentencing, we look first to whether the sentencing court imposed a “sentence exceeding the maximum allowed based only on the facts found by the jury.” United States v. Hughes, 401 F.3d 540, 546, 2005 WL 628224, at *5 (4th Cir. Mar.16, 2005). More specifically, we must assess whether the sentencing court’s enhancement fits within the “fact of a prior conviction” exception of Apprendi and Booker.
2.
The “fact of a prior conviction” exception specified in Apprendi originated in Almendarez-Torres v. United States, 523 U.S. 224, 118 S.Ct. 1219, 140 L.Ed.2d 350 (1998). In that case, the Court addressed the appeal of an alien who had pleaded guilty to re-entering the United States illegally after his deportation, in contravention of 8 U.S.C. § 1326. A subsection of that statute authorized a sentence of up to twenty years for an alien who illegally returned to this country after having previously been deported following an aggravated felony. See 8 U.S.C. § 1326(b)(2). The Court determined that the failure of the indictment to allege the defendant’s prior aggravated felonies and the applicability of subsection (b)(2) neither contravened the Sixth Amendment nor implicated due process concerns, because the statutory provision was simply a penalty provision to be applied by a sentencing judge in a post-conviction setting' — ie., it was not a separate offense. Almendarez-Torres, 523 U.S. at 233-36, 118 S.Ct. 1219.
In Apprendi, 530 U.S. at 490, 120 S.Ct. 2348, the Court enunciated its holding that “[ojther than the fact of a prior conviction, any fact that increases the penalty for a crime beyond the prescribed statutory maximum must be submitted to a jury, and proved beyond a reasonable doubt.” Apprendi, 530 U.S. at 490, 120 S.Ct. 2348. In explaining this rule, the Court in Apprendi limited its ruling in Almendarez-Torres, pointing to two factors that distinguished Almendarez-Torres’s case: “the certainty that procedural safeguards attached to any ‘fact’ of prior conviction” and “the reality that Almendarez-Torres did not challenge the accuracy of that fact in his case.” Id. at 488, 120 S.Ct. 2348. Together, these factors “mitigated the due process and Sixth Amendment concerns otherwise implicated in allowing a judge to determine a ‘fact’ increasing punishment beyond the maximum of the statutory range.” Id.
3.
In its recent Shepard decision, the Court addressed the application of the prior conviction exception to a disputed fact “about a prior conviction.” 125 S.Ct. at 1262 (emphasis added). Shepard, who was convicted under 18 U.S.C. § 922(g), initially faced a maximum sentence, under the Guidelines, of thirty-seven months; however, the Government sought to increase his sen[840]*840tence to the fifteen-year mandatory minimum of § 924(e), which applies to felons with three prior drug or violent felony convictions. Shepard had three prior burglary convictions, and the Government maintained that those burglaries constituted “violent felonies.” Shepard, 125 S.Ct. at 1258.
In making this contention, however, the Government ran afoul of Taylor v. United States, 495 U.S. 575, 110 S.Ct. 2143, 109 L.Ed.2d 607 (1990), where the Court had earlier determined that a “violent felony,” pursuant to 18 U.S.C. § 924(e), includes only the burglary of a structure or building (“generic burglary”), not other types of burglary, such as burglaries of cars or vessels.5 The burglary statute of Massachusetts, where Shepard’s three earlier convictions occurred, is broader than generic burglary, and can also include burglary of a non-structure, such as a car or vessel. Shepard’s indictment did not specify whether burglary of a structure, ie., generic burglary, was at issue in his convictions. As a result, the First Circuit instructed the sentencing court to answer this question by looking to the relevant complaint applications and police reports. United States v. Shepard, 348 F.3d 308, 310-11 (1st Cir.2003), vacated by — U.S. -, 125 S.Ct. 1254, 161 L.Ed.2d 205 (2005).6 The Supreme Court granted cer-tiorari and reversed the First Circuit. In so doing, the Court reiterated its holding-in Taylor that a sentencing court addressing § 924(e) cannot consider items from the record of a prior conviction that were not conclusively validated in the earlier proceeding. Shepard, 125 S.Ct. at 1260-61.
An opinion authored by Justice Souter in Shepard and joined by three other Justices (of the eight participating),7 characterized Taylor’s statutory construction rule as of Sixth Amendment significance. The plurality opinion first explained that a burglary conviction rendered in a generic burglary state inherently identifies the offense as a “violent felony,” and the “judicial finding of a disputed prior conviction is made on the authority of Almendarez-Torres.” Shepard, 125 S.Ct. at 1262. However, when the definition of the prior crime itself does not reveal whether the conviction was for generic burglary, as Justice Souter explained, the “only certainty of a generic finding lies in jury instructions, or bench trial findings and rulings, or (in a pleaded case) in the defendant’s own admissions or accepted findings of fact confirming the factual basis for a valid plea.” Id.
A sentencing court’s consideration of materials beyond those documents identified by the Court, the Shepard plurality advised, “raises the concern underlying Jones and Apprendi.” Id. It deemed “debatable” which, if any, facts contained in such additional documents were part of what the state court was “required to find” as a basis for the earlier conviction. Id. If the sentencing court were to determine which facts the state court was “required to find” as part of the judgment, the sen[841]*841tencing court would “make a disputed finding of fact about what the defendant and state judge must have understood as the factual basis of the prior plea.” Id. Such a “disputed fact ... about a prior conviction” is “too far removed from the conclusive significance of a prior judicial record, and too much like the findings subject to Jones and Apprendi to say that Almenda-rez-Torres clearly authorizes a judge to resolve the dispute.” Id. As a result, Justice Souter’s plurality opinion advised that the Court’s construction of § 924(e) is “necessary to avoid serious risks of unconstitutionality.” Id. at 1263.
Justice Thomas’s concurring opinion announced an even stronger view: that a sentencing court’s reliance on items beyond the charging papers in the earlier case would give rise not merely to constitutional doubt, but to constitutional error. See Shepard, 125 S.Ct. at 1263-64 (Thomas, J., concurring in part and concurring in the judgment). A majority of the Shepard Court thus agreed that any inquiry beyond charging documents and the like, in the context of the application of § 924(e), at the very least raises “serious” constitutional “risks.”
B.
Washington’s case raises the issue of the scope and substance of the Sixth Amendment “risks” identified in Shepard. The sentencing court increased Washington’s sentence above that authorized by his earlier guilty plea to the breaking and entering charge alone, and did so based on its determination that Washington’s conviction was for a “crime of violence,” because it “otherwise involve[d] conduct that presents a serious potential risk of physical injury to another.” USSG § 4B1.2(a)(2). In making this determination, the sentencing court relied on facts outside the indictment containing the prior breaking and entering offense. As applied to Washington’s appeal, the Apprendi line of decisions mandates the conclusion that this procedure involved more than the “fact of a prior conviction” exempted by Apprendi from Sixth Amendment protection. Accordingly, as explained below, Washington’s sentence was imposed in violation of his Sixth Amendment rights.8
The sentencing court relied on facts outside the indictment in concluding that Washington’s prior offense was a crime of violence. Although the court began with the conduct expressly charged — Count 1 of Washington’s earlier indictment — the court then found additional facts about the building that was subjected to the break-in.9 These facts included what, from the court’s common experience, the building’s likely contents were; the identity of any occupants; and the probable level of security. These additional, hypothetical facts were specific: e.g., that “drugs and guns” would [842]*842be present on the premises; that such items would be “protected from theft”; that, “even if no one affiliated with the Task Force was present at the time” of the break-in, “one or more members or employees” could “show up there at any time of day or night in view of the oft-times clandestine and nocturnal nature of their work”; and that any such employee “would be armed.” While the court characterized these facts as arising from its common experience, they echoed the extra-indictment information presented by the Government.10
Significantly, the additional facts found and relied upon by the sentencing court were nowhere alleged in Washington’s state court indictment. That indictment merely identified the building as one occupied by the Midwestern Drug and Violent Crime Task Force. Importantly, it did not reveal whether the Task Force office consists of bureaucratic administrators or police officers, or the nature of property contained therein — e.g., computers and files or drugs and guns.
In these circumstances, the sentencing court relied on facts outside of the prior indictment and resolved a disputed fact “about a prior conviction,” see Shepard, 125 S.Ct. at 1262 (emphasis added)— namely, that the prior conviction was one which “otherwise involve[d] conduct that presents a serious potential risk of physical injury to another.” USSG § 4B1.2(a)(2). These findings are “too far removed from the conclusive significance of a prior judicial record,” and “too much like the findings subject to Jones and Ap-prendi,” Shepard, 125 S.Ct. at 1262, “to say that Almendarez-Torres clearly authorizes a judge to resolve the dispute,” id. This process and its results thus raise the very “risk” identified in Shepard, that Sixth Amendment error occurred.
The question before us concerns whether the “risk” identified by the Court in Shepard was actually realized here — that is, whether the sentencing court’s use of extra-indictment facts contravened Washington’s Sixth Amendment rights. And, as explained below, we are constrained to conclude that it was.
There is no question that the extra-indictment facts relied on by the sentencing court, and its conclusion that Washington’s prior offense constituted a “crime of violence,” were not necessarily determined in the earlier proceeding. Washington pleaded guilty to the breaking and entering count of the prior indictment only, and no judicial determination was made that Washington had committed larceny — much less what, if anything, was stolen from (and therefore contained in) the building. Washington’s prior guilty plea in no way implicated the level of the building’s security system, the nature of its employees and their activities, or whether they at times return to work at night. As a result, the foregoing aspects of the prior convic[843]*843tion, which were relied upon by the sentencing court to enhance Washington’s base offense level, were not part of what the state court was “required to find” as part of Washington’s conviction. Shepard, 125 S.Ct. at 1262.
Furthermore, the special circumstances identified by the Court in Almendarez-Torres are not present here. See Apprendi, 530 U.S. at 488, 120 S.Ct. 2348 (noting that Almendarez-Torres admitted that his prior conviction was for an “aggravated felony”). Washington contests both the additional facts relied upon by the sentencing court, and the court’s conclusion, based on those facts, that his prior conviction was a “crime of violence” because it “otherwise involved conduct that presented a serious risk of potential physical injury to another.” Washington has not waived this issue, Shepard, 125 S.Ct. at 1262, and the “procedural safeguards” concern of the Apprendi line of decisions thus have not been satisfied. See Apprendi 530 U.S. at 488, 120 S.Ct. 2348. As a result, the sentencing court’s reliance on extra-indictment facts in concluding that Washington’s prior offense constituted a “crime of violence” resulted in an enhancement to Washington’s sentence based on more than the “fact of’ his prior conviction. See Shepard, 125 S.Ct. at 1262-63. A Sixth Amendment error thus occurred.
C.
In conclusion, the sentencing court’s application of the crime of violence enhancement of §§ 2K2.1(a)(4) and 4B1.2(a) of the Sentencing Guidelines in Washington’s sentencing proceedings was error under Booker and Shepard. And, even though both those decisions were rendered by the Supreme Court after Washington was sentenced, the error was nonetheless “plain” at the time of our appellate review. See Johnson v. United States, 520 U.S. 461, 468, 117 S.Ct. 1544, 137 L.Ed.2d 718 (1997) (finding that an error is plain “where the law at the time of trial was settled and clearly contrary to the law at the time of appeal”). The sentencing court’s application of § 2K2.1(a)(4) in Washington’s case resulted in at least nine months of additional imprisonment for him. In these circumstances, “the sentence imposed by the district court as a result of the Sixth Amendment violation was longer than that to which he would otherwise be subject,” Hughes, 401 F.3d at 548, 2005 WL 628224, at *6 (quoting United States v. Angle, 254 F.3d 514, 518 (4th Cir.2001) (en banc)), and the sentence contravened Washington’s substantial rights. See Hughes, 401 F.3d at 548, 2005 WL 628224, at *5-6; accord United States v. Promise, 255 F.3d 150, 160 (4th Cir.2001) (en banc) (holding that Apprendi error resulting in increased sentence affects defendant’s substantial rights). Finally, consistent with Hughes, to leave standing Washington’s sentence, which was at least nine months longer than he could have received without the error, would place in jeopardy the fairness, integrity, or public reputation of judicial proceedings. Hughes, 401 F.3d at 555, 2005 WL 628224, at *13; see also United States v. Washington, 398 F.3d 306, 312-13 (4th Cir.2005) (recognizing error resulting in five months extra imprisonment).
IV.
Pursuant to the foregoing, we vacate Washington’s sentence and remand for such other and further proceedings as may be appropriate.
VACATED AND REMANDED