OPINION OF THE COURT
MANSMANN, Circuit Judge.This appeal requires us to consider whether the defendant’s indictment for fed*598eral narcotics violations under 21 U.S.C. § 846 and § 841(a) provided him with notice to support the imposition of an enhanced penalty provision under § 841(b)(6) for possession with intent to distribute in excess of 1,000 pounds of marijuana. We conclude that 21 U.S.C. § 841(b)(6) is an enhanced penalty provision and not a separate crime. We find that the indictment at issue put the defendant Stephen Gibbs on notice of the possibility that an enhanced sentence might be imposed. Accordingly, we will affirm the judgment of the district court.
I.
In 1981 the defendant Stephen Gibbs and five others were charged with conspiracy (in violation of 21 U.S.C. § 846) to distribute and possess with intent to distribute marijuana (in violation of 21 U.S.C. § 841(a)(1)). Although the indictment contained three counts, Gibbs was charged in only one count of the indictment. Gibbs was subsequently convicted of a conspiracy to violate the federal narcotics laws, namely 21 U.S.C. § 841(a)(1) which provides:
(а) Except as authorized by this subchapter, it shall be unlawful for any person knowingly or intentionally—
(1) to manufacture, distribute, or dispense, or possess with intent to manufacture, distribute, or dispense, a controlled substance; 21 U.S.C. § 841(a)(1).
Pursuant to the Penalties provisions of § 841, Gibbs was sentenced under § 841(b)(6), which provides in relevant part:
(б) In the case of a violation of subsection (a) of this section involving a quantity of marihuana exceeding 1,000 pounds, such person shall be sentenced to a term of imprisonment of not more than 15 years, and in addition, may be fined not more than $125,000____
21 U.S.C. § 841(b)(6) (1982). Gibbs’ sentence was for a period of ten years imprisonment, which is greater than the regular sentence which may be imposed for a marijuana violation.1
Gibbs' initial appeal, which challenged the prerequisites for the admission into evidence of co-conspirator testimony and asserted that the introduction of that testimony violated his sixth amendment right to confront and cross-examine witnesses, was heard by a panel of this court, which reversed his conviction on March 22, 1983. On the government’s petition for rehearing in banc, we reinstated Gibbs’ conviction. United States v. Gibbs, 739 F.2d 838 (3d Cir.1984), cert. denied, 469 U.S. 1106, 105 S.Ct. 779, 83 L.Ed.2d 774 (1985) (“Gibbs I”). Gibbs’ petition for rehearing in banc was denied.
Gibbs subsequently filed a Motion to Correct Illegal Sentence and a Motion to Vacate or Correct Sentence pursuant to 28 U.S.C. § 2255. The district court denied the Motion to Correct Illegal Sentence, denied the claims pursuant to 28 U.S.C. § 2255 relating to the sentence, and held in abeyance the claim relating to ineffective assistance of counsel. This appeal followed.
II.
Gibbs now asserts on appeal that imposition of the enhanced penalty violates the ex post facto clause of the Constitution, and that the evidence at trial was insufficient to support his sentence. Gibbs primarily contests, however, the sufficiency of the indictment to support the imposition of the enhanced penalty under § 841(b)(6). *599We turn first to the issue involving the indictment.
The final paragraphs of Count One of the indictment read:
(e) On or about October 5, 1980, the defendant Joseph Quintiliano had a telephone conversation with the defendant Stephen Gibbs to arrange for Gibbs to purchase the plane-load of marijuana.
(f) In or about about the early morning of October 6, 1980, because of a shortage of fuel, the defendant Prentiss C. Breland landed the Beechcraft Queen Air airplane at an airport near Boca Raton, Florida, with 1,487 pounds of marijuana.
Gibbs argues that because the indictment did not specifically charge him with either conspiracy to possess an amount of marijuana in excess of 1,000 pounds, or with a violation of 21 U.S.C. § 841(b)(6), imposition of the enhanced penalty under § 841(b)(6) is impermissible. He contends that the amount of marijuana is an essential element of the offense with which he was charged and that failure to charge him with that element denied him fair notice in preparing and presenting his defenses. In addition, Gibbs argues that the issue of the quantity of the marijuana must be submitted to the jury and must be proved beyond a reasonable doubt.
The government contends that § 841(b)(6) is simply an enhanced penalty provision and not an element of the crime. The prosecution argues, therefore, that the defendant is not entitled to notice in the indictment that a heavier sentence may be imposed. In the alternative, the government contends that because the indictment specified that 1,487 pounds of marijuana were in the plane, the defendant was on notice that he was subject to the heavier penalties of § 841(b)(6).
Our standard of review concerning the adequacy of the indictment to support the enhanced penalty is plenary as this involves an issue of law. See United States v. Adams, 759 F.2d 1099 (3d Cir.1985), cert. denied, — U.S. -, 106 S.Ct. 336, 88 L.Ed.2d 321 (1985). As we noted in United States v. Sebetich, 776 F.2d 412 (3d Cir. 1985), an indictment provides satisfactory protection to a defendant if it fairly informs him of the charge and enables him to plead acquittal or conviction in bar of future prosecutions for the same offense.
Our task here is to determine whether sufficient notice for such protection was given in the indictment filed in this case. Although the indictment did not specifically mention § 841(b)(6), we find that the indictment as a whole fairly informed Gibbs of the amount of marijuana with which he was charged pursuant to § 841(a)(1), and which would subject him to the enhanced penalty provision of § 841(b)(6). Because we conclude that Gibbs did receive notice, we need not, and do not, decide whether the enhanced sentence could stand in the absence of notice in the indictment. We do, however, agree with the government’s position that § 841(b)(6) is a penalty enhancement provision and not a separate crime. That specific issue has divided the courts of appeals.
In United States v. Normandeau, 800 F.2d 953 (9th Cir.1986), the appellants contended that knowledge of the amount of marijuana involved is an element of the aggravated offense. In holding that contention invalid and in finding that § 841(b)(6) is merely a penalty provision, the Court of Appeals for the Ninth Circuit concluded that
[Pjroof that an accused knew how much marijuana was involved is not an element of a section 841(a) offense. Through their involvement in the illegal transaction, defendants assumed the risk of enhanced penalties if the government could show that their offense involved more than 1,000 pounds of marijuana.
Normandeau, 800 F.2d at 956. The court declined to decide the issue of whether the indictment must allege that more than 1,000 pounds of marijuana is involved before increased penalties could be sought, finding that the indictment before it clearly alleged that more than 1,000 pounds was involved and cited § 841(b)(6).
Similarly, the Court of Appeals for the First Circuit has held that proof of the amount of marijuana is an essential ele*600ment only under § 841(b)(6). United States v. McHugh, 769 F.2d 860 (1st Cir.1985). There, the court pointed out that neither § 841(a) nor § 846 (the general conspiracy section) requires any specific quantity for conviction. Section 841(b) merely specifies the penalties for violations of § 841(a), depending on the substance and quantity involved.
That § 841(b)(6) is a penalty which was intended to apply to conspiracies as well as to actual possession was explained in United States v. Wright, 742 F.2d 1215 (9th Cir.1984). The court reasoned that § 841(b)(6) can apply to. any § 841(a) offense (involving more than 1,000 pounds of marijuana), and § 846 prohibits attempts or conspiracies to commit the substantive acts prohibited by § 841(a). Since the penalty for conspiracy may not exceed the maximum punishment prescribed for the commission of the offense which was the object of the conspiracy, a person convicted of attempting or conspiring to violate § 841(a) is subject to the maximum penalty for the offense. That penalty may be the one specified under § 841(b)(6) if the offense involves more than 1,000 pounds of marijuana.
Consistent with McHugh and Wright is the analysis of the Court of Appeals for the Eleventh Circuit in United States v. Simmons, 725 F.2d 641 (11th Cir.1984), cert. denied, 469 U.S. 827, 105 S.Ct. 108, 83 L.Ed.2d 52 (1984). In Simmons, the court differentiated § 841(a) which declares unlawful the possession with intent to distribute a controlled substance, with § 841(b)(6) which authorizes an enhanced penalty if that controlled substance is marijuana in excess of 1,000 pounds. The court theorized that the substantive crime could be proved without any consideration of the amount involved, but if the proof at trial showed possession of more than 1,000 pounds of marijuana, the enhanced penalty provision would come into play. The court held that the 1,000 pound provision was, therefore, only applicable to the sentencing phase. Simmons, 725 F.2d at 643-44.
We recognize that the courts in these cases were not required to answer the question before us (i.e., was notice of the possibility of an enhanced penalty given) because those indictments arguably listed § 841(b)(6). Nonetheless, it is instructive that the courts utilized the premise that § 841(b)(6) is an enhanced penalty provision rather than a separate crime in resolving related and more sophisticated issues. We find persuasive the analyses indicating that § 841(b) is merely a penalty provision to be used at sentencing, after conviction of the substantive crime.
The defendant primarily relies on United States v. Alvarez, 735 F.2d 461 (11th Cir.1984), to support his contention that the quantity of the substance is an element of a separate crime for which an enhanced penalty may be imposed. In Alvarez, the court held that
[T]he present indictment cannot properly serve as the basis for sentences in excess of the five years specified in 21 U.S.C. § 841(b)(1)(B). Since the quantity of the substance constitutes a critical element of the offense under 21 U.S.C. § 841(b)(6), and no quantity of marijuana was specifically alleged in the indictment, the enhanced sentences imposed pursuant to that provision are invalid.
Alvarez, 735 F.2d at 468.
Gibbs’ reliance on Alvarez is misplaced. We do not read Alvarez to hold that the amount of marijuana is an essential element of the substantive offense charged. Rather, Alvarez is more properly read to require an allegation of value, or quantity, in the indictment, before an enhanced penalty may be imposed. Under the facts in Alvarez, the indictment alleged no specific amount of marijuana, and the issue in that case was whether that indictment could support the enhanced penalty. The court found § 841(b)(6) to be a “penalties” section, which enumerated “for sentencing purposes, specific considerations to be given to the type and quantity of the substances.” Alvarez, 735 F.2d at 461. Finding no allegation of the amount of marijuana in the indictment, the court would not validate the enhanced penalty which had been imposed.
*601An opposing view has been taken by the Court of Appeals for the District of Columbia in United States v. Moore, 540 F.2d 1088 (D.C.Cir.1976). There, the court discussed the legality of an enhanced sentence under 21 U.S.C. § 845(a) which provides for greater punishment for distributing a controlled substance to a person under 21 years of age. The court found that the age of the distributee was an aggravation arising from the manner in which the crime was committed, thereby constituting a new offense. The court concluded that Congress sought to punish activity which would constitute a different element of distributing and required an allegation in the indictment before the greater sentence could be imposed.
We distinguish United States v. Moore on the basis that § 845(a) is in itself the separate offense of “distribution to a minor.” It is not a category of a penalty section for possession and distribution of controlled substances as is § 841(b)(6).
III.
We find that the indictment against Stephen Gibbs satisfies both parts of the tests outlined in Sebetich, 776 F.2d 412, requiring satisfactory notice of the charge, and enabling a defendant to properly plead in bar of further prosecution for the same offense. Count One of the indictment, the only count in which Gibbs was named, specifically recites a violation of 21 U.S.C. § 841(a)(1). The language of the indictment tracks the language of the statute in sufficient detail to leave no question of the nature of the charge against Gibbs. In at least two places the indictment recites the phrase “marihuana, a Schedule I controlled substance.” The use of that phrase is relevant in regard to the penalties section of 21 U.S.C. § 841(b).
In § 841(b), the penalties are enumerated according to the schedule on which the controlled substance is listed. If the controlled substance is marihuana, § 841(b)(1)(B) defines the penalty by further reference to the special penalty provisions of § 841(b)(4), (5) and (6). The last of these is the enhanced penalty provision for a violation involving a quantity of marijuana exceeding one thousand pounds.
The final paragraphs of Gibbs’ portion of the indictment clearly allege that the marijuana involved was in excess of one thousand pounds. Under these circumstances we find that the offense was described with sufficient particularity to put the defendant on notice of the full nature of the charge against him including the possibility that the enhanced penalty provision for marijuana in excess of 1,000 pounds could be imposed. When the four comers of the indictment are read in their entirety, it is obvious that the penalty provision of (6) could be invoked. It is immaterial that the penalty section was not specifically cited. By virtue of the fact that the indictment charged a conspiracy in violation of § 846 and announced the amount of marijuana involved, Gibbs was fairly informed that he was charged with a violation of § 841(a) involving a quantity of marijuana exceeding 1,000 pounds.
The second element of the Sebetich test requires protection from double jeopardy, that is, the accused must not be twice subject to the same offense. In this case, the indictment stated what the defendant was alleged to have done, and when, where and how he was alleged to have done it. Sebetich, 776 F.2d 412. The indictment enumerates the means used by the defendants and co-conspirators to further the object of the conspiracy and describes a series of overt acts allegedly taken in furtherance of this conspiracy. We find therefore that the indictment properly protected Gibbs from double jeopardy.
IV.
Gibbs argues as well that imposition of the enhanced penalty violates the ex post facto clause of the Constitution. He contends that most of the events of this conspiracy antedated the penalty provision at issue, and that in the absence of a special verdict the jury may not have found any participation in the conspiracy by Gibbs after the effective date of the statute.
*602The ex post facto clause prohibits the imposition of a law which purports to make innocent acts criminal after their event, or to aggravate an offense by altering the amount of punishment imposed for its commission, after the fact, to the disadvantage of the accused.
The enhanced penalty provision at issue here became effective on September 26, 1980, while the conspiracy charged began in the Spring of 1979 and ended on or about October 6, 1980. On its face then, § 841(b)(6) was applicable to all acts and offenses occurring after September 26, 1980.
Gibbs’ indictment specifically alleged that on or about April 7, 1980 he discussed buying marijuana with a co-conspirator, that on October 5, 1980 he had a telephone conversation relative to the planeload of marijuana and that on October 6, 1980 the airplane landed with 1,487 pounds of marijuana. At trial, the government offered evidence of Gibbs’ participation in the conspiracy beginning in April, 1980. In reviewing the district court’s determination that a preponderance of independent evidence established Gibbs’ participation at that time, we held that the evidence permitted a reasonable inference of Gibbs’ complicity in the enterprise. Gibbs I, 739 F.2d at 843-44. Once the government establishes a defendant’s involvement in an ongoing conspiracy, the burden shifts to the defendant to prove by affirmative acts inconsistent with the object of the conspiracy that he withdrew. United States v. Ammar, 714 F.2d 238 (3d Cir.1983), cert. denied, 464 U.S. 936, 104 S.Ct. 344, 78 L.Ed.2d 311 (1983). We held in Gibbs I that because there was no evidence that Gibbs withdrew from the conspiracy after April, his involvement could be deemed to have continued until October. Gibbs I, 739 F.2d at 845.
Since Gibbs’ involvement continued after the effective date of § 841(b)(6), that statute is applicable to the events of October, 1980. In addition a statutory change which takes effect during the existence of an ongoing conspiracy will subject members of that conspiracy to the provisions of the later enactment. See, e.g., United States v. Wells Fargo Armored Car Service Corp., 587 F.2d 782 (5th Cir.1979). Thus, § 841(b)(6) was applicable to the acts and offense alleged here.
V.
Gibbs argues that because there is no specific finding by the jury on the amount of marijuana proven by the government, the conviction cannot support the enhanced sentence and that the evidence is insufficient to support a conspiracy to possess over 1,000 pounds of marijuana.
Our standard of review on the denial of a motion to correct illegal sentence is narrow. We will not disturb a ruling on such a motion except for a clear abuse of discretion. United States v. Bickoff, 531 F.2d 182 (3d Cir.1976). Moreover, the district court has wide latitude in imposing a sentence within the statutory limits. United States v. Matthews, 773 F.2d 48 (3d Cir.1985.)
In considering Gibbs’ more specific argument that the government was required to prove that he knew that the conspiracy was one to possess with intent to distribute in excess of 1,000 pounds of marijuana, we note that this is a variant of his argument that the enhanced penalty provision is a separate element of the offense.
Assuming without deciding that the government was required to prove additionally his specific knowledge that the conspiracy encompassed an amount of marijuana in excess of 1,000 pounds, we find that the trial record clearly supports the fact that over 1,000 pounds of marijuana was involved, and that Gibbs had knowledge that the amount of marijuana involved was in excess of 1,000 pounds.
The trial testimony indicated that as early as April, 1980, Gibbs knew that an airplane was to be used to transport the marijuana to the United States, was in frequent contact with his co-conspirators, and that he was the intended buyer of the marijuana. The trial testimony also indicated that in early October, 1980 Gibbs indicated over the telephone that he had only one hundred *603thousand dollars with which to buy the marijuana, that he would get the remaining money to a co-conspirator within a few days, and that he would try to make the necessary arrangements to have someone come down to pick up the delivery.
At trial, Michael Dusenberry, a detective in the organized crime unit of the City of Boca Raton, Florida, testified that he had searched the Beechcraft airplane on October 5, 1980, and that 23 bales of suspected marijuana were removed from the airplane and taken to an evidence locker at the police department. It was stipulated at trial that Jay Pintacuda, forensic chemist of the Sheriff’s Office at Palm Beach County, Florida, would have testified that core samples taken from the 23 seized bales of suspected marijuana contained cannabis, a Schedule I controlled substance. Most important, it was never disputed at trial that the amount of marijuana involved was in excess of 1,000 pounds. The jury could clearly infer from this testimony that Gibbs knew that the amount of marijuana was substantial and indeed, in excess of 1,000 pounds. Given our holding that the amount of marijuana is a factor bearing upon sentencing, rather than guilt, we find Gibbs’ arguments on these issues merit-less. We also note that at sentencing Gibbs did not dispute the amount of marijuana nor offer any evidence otherwise.
The defendant’s judgment of conviction will be affirmed.
. Gibbs was sentenced on February 8, 1982. Section 841(b)(6) was repealed on October 12, 1984, Pub.L. 98-473, Tit. II, § 502(5). The current statute provides that:
(B) In the case of a controlled substance in schedule I or II except as provided in subparagraphs (A) and (C), such person shall be sentenced to a term of imprisonment of not more than 15 years; a fine of not more than $125,-000, or both____
(C) In the case of less than 50 kilograms of marijuana ... such person shall ... be sentenced to a term of imprisonment of not more than 5 years, a fine of not more than $50,000 or both.
21 U.S.C. § 841(b)(1)(C) (1986). Thus Congress has expanded the potential for an enhanced penalty for violations of § 841(a) from one involving in excess of 1,000 pounds of marijuana, to one involving in excess of 50 kilograms of marijuana (approximately 110 pounds).