¶1Robert A. Butterworth, Atty. Gen., Department of Legal Affairs, Susan A. Maher, Asst. Atty. Gen., Tallahassee, Fla., for respondents-appellants.
¶2Bava Harrison, Tallahassee, Fla., for petitioner-appellee.
¶3*1497Before TJOFLAT and EDMONDSON, Circuit Judges, and ATKINS *, Senior District Judge.
¶6Under Florida law, a prisoner who behaves well and diligently performs assigned work can reduce his term of incarceration by earning “gain time.” In the district court, petitioner Jeffrey Raske, an inmate in the Florida prison system, sought a writ of habeas corpus, claiming that a 1983 Florida statute which altered the amount and calculation of gain time constituted an unconstitutional ex post facto law as applied to prisoners such as himself who were convicted of offenses that occurred prior to the statute’s passage. See U.S. Const, art. I, § 10, cl. 1 (“No State shall ... pass any ... ex post facto Law_”).1 The district court granted the writ, and the State of Florida now appeals. We affirm.
¶7I.
¶8Raske is presently serving three concurrent twenty-five year prison sentences imposed by the circuit court of Broward County, Florida, for a series of robberies that occurred in 1982.2 At the time of Raske’s offenses, Florida law provided the following formula for the calculation of gain time:
(1) The [Department of Correction] shall grant the following deductions for gain-time on a monthly basis, as earned, from the sentences of every prisoner who has committed no infraction of the rules of the department or of the laws of the state and who has performed in a satisfactory and acceptable manner the work, duties, and tasks assigned, as follows:
(a) Three days per month off the first and second years of the sentence;
(b) Six days per month off the third and fourth years of the sentence; and
(c) Nine days per month off the fifth and all succeeding years of the sentence ....
[(2)](b) The department is authorized to grant additional gain-time allowances on a monthly basis as earned up to one day for each day of productive or institutional labor performed by any prisoner ... who has accomplished in a satisfactory and acceptable manner, the work, duties, and tasks assigned. Such gain-time allowances under this section shall be awarded on the basis of diligence of the inmate, the quality and quantity of work performed, and the skill required for performance of the work.
(3)(a) An inmate who faithfully performs the assignments given to him in a conscientious manner over and above that which may normally be expected of him ... may be granted on an individual basis from one to six days per month extra gain-time to be deducted from the term of his sentence.
¶9Act of June 16, 1978, ch. 304, § 1, 1978 Fla.Laws 870, 870-71 (codified, as amended, at Fla.Stat. § 944.275 (1979-1981)) [hereinafter the 1978 act].3 Thus, under the 1978 act, prisoners who diligently performed their assigned duties could earn up to forty-six days of gain time each month.4
¶10*1498In 1983, the Florida legislature amended section 944.275 to provide as follows:
(1) The [department] is authorized to grant deductions from sentence in the form of gain-time to encourage satisfactory prisoner behavior, to provide incentive for prisoners to participate in productive activities and to reward prisoners who perform outstanding deeds or services.
(4)(a) As a means of encouraging satisfactory behavior, the department shall grant basic gain-time at the rate of 10 days for each month of each sentence imposed on a prisoner....
(b) For each month a prisoner works diligently ... the department may grant up to 20 days of incentive gain-time, which shall be credited and applied monthly.
(5) When a prisoner is found guilty of an infraction of the laws of this state or the rules of the department, gain-time may be forfeited according to law.
¶11Correctional Reform Act of 1983, ch. 131, § 8, 1983 Fla.Laws 442, 442-43 (codified at Fla.Stat. § 944.275 (1987)) [hereinafter the 1983 act]. Compared to the 1978 provisions, the 1983 act increased the amount of basic gain time inmates could earn for general good behavior from a three/six/nine day variable rate to ten days per month; the potential incentive gain time available to prisoners, however, decreased from thirty-seven to twenty days per month.
¶12The department has applied the method of calculating gain time adopted in the 1983 act to all inmates — including those convicted of offenses that occurred before the act’s passage. See Fla.Admin.Code Ann. r. 33-11.0065 (1988) (making no distinction between pre- and post-act offenders). The State admits that under the 1978 gain time system, petitioner’s estimated release date is September 13, 1995 and that under the 1983 act, petitioner’s estimated release date is April 5, 1997.
¶13II.
¶14Our decision in this case is controlled by the principles announced by the Supreme Court in Weaver v. Graham, 450 U.S. 24, 101 S.Ct. 960, 67 L.Ed.2d 17 (1981). In that case, the Court was also faced with legislative alterations to the method by which the department calculated gain time for Florida prisoners. Under a 1963 Florida statute, gain time was awarded as follows:
(1) The [department] shall grant the following deductions for gain time from the sentences of every prisoner who has committed no infraction of the rules or regulations of the board or the division, or of the laws of the state, and who has performed in a faithful, diligent, industrious, orderly, and peaceful manner, the work, duties, and tasks assigned to him, to-wit:
Five (5) days per month off the first and second years of his sentence;
Ten (10) days per month off the third and fourth years of his sentence; and
Fifteen (15) days per month off the fifth and all succeeding years of his sentence. ...
¶15Act of May 31, 1963, ch. 243, § 1, 1963 Fla.Laws 547, 548 (codified, as amended, at Fla.Stat. § 944.27(1) (1963-1977)) [hereinafter the 1963 act]. In 1978, this five/ten/fifteen day scheme was changed to the three/six/nine day system described above. See Act of June 16, 1978, ch. 304, § 1, 1978 Fla.Laws 870, 870-71. A Florida prisoner challenged the constitutionality of the 1978 gain time provision, claiming that the law was ex post facto as applied to individuals such as himself who committed offenses before the effective date of the 1978 act. The Court agreed, concluding that “the new provision constricts the inmate’s opportunity to earn early release, and thereby makes more onerous the punishment for crimes committed before its enactment. This result runs afoul of the prohibition against ex post facto laws.” Weaver, 450 U.S. at 35-36, 101 S.Ct. at 968 (footnote omitted).
¶16*1499Although the facts in Weaver are on all fours with the facts of the instant case, the State makes three arguments as to why the 1983 act is not ex post facto as applied to petitioner. We consider them in turn.
¶17A.
¶18The State first advances several arguments that attempt to distinguish between the unconstitutional provisions of the 1978 act, which reduced the amount of basic gain time available to inmates, and the provisions of the 1988 act, which reduce the availability of incentive gain time. These arguments center on the State’s contention that basic gain time is “automatic,” while incentive gain time is “discretionary.”
¶191.
¶20The State contends that basic gain time is fundamentally different than incentive gain time because basic gain time is automatically earned by prisoners, while incentive gain time is earned only at the discretion of prison officials. Because incentive gain time is discretionary in nature, the State contends that petitioner has no right to receive incentive gain time and that the State therefore can alter the method by which incentive gain time is calculated without violating the ex post facto clause of the Constitution.5 Because we believe that both basic and incentive gain time are discretionary in nature, we do not find the State’s argument to be persuasive.6
¶21An examination of the statutory language authorizing basic gain time reveals that a prisoner must satisfy certain conditions in order to receive basic gain time and that the department is the judge of whether those conditions have been met. Thus, the 1963 act provided that basic gain time would be awarded only to prisoners who performed their duties “in a faithful, diligent, industrious, orderly, and peaceful manner.” Act of May 31, 1963, ch. 243, § 1, 1963 Fla.Laws at 548. Similarly, the 1978 act allowed the department to award basic gain time only if the prisoner “performed in a satisfactory and acceptable manner the work, duties, and tasks assigned.” Act of June 16,1978, ch. 304, § 1, 1978 Fla.Stat. at 870. Finally, we note that although the 1983 act does automatically give prisoners ten days of gain time, that gain time can be forfeited if, among other things, the prisoner “neglect[s] to perform the work duties, and tasks assigned to him in a faithful, diligent, industrious, orderly, and peaceful manner.” Fla.Stat. § 944.28(2)(a) (1987).7
¶22We see no fundamental distinction between the conditions that a prisoner must satisfy to receive basic gain time and the conditions that a prisoner must satisfy to earn discretionary gain time. In both cases, the department decides in its sole discretion whether the prisoner has behaved well enough or worked diligently enough to earn gain time. We therefore reject the State’s attempt to distinguish the 1983 act from the 1978 act at issue in Weaver by a supposed distinction between the nature of basic and incentive gain time.
¶232.
¶24In a second argument, the State contends that incentive gain time is discretionary *1500because the duties that allow a prisoner to earn such gain time are a matter of legislative grace. See, e.g., Newman v. Alabama, 559 F.2d 283, 292 (5th Cir.1977) (Constitution does not mandate that states provide inmates with work.). We agree that in this sense incentive gain time could be characterized as discretionary.8 Such a characterization, however, does not prevent the 1983 act from being ex post facto as applied to the petitioner.9
¶25In Weaver, the Supreme Court stated clearly that “even if a statute merely alters penal provisions accorded by the grace of the legislature, it violates the [ex post facto clause] if it is both retrospective and more onerous than the law in effect on the date of the offense.” Weaver, 450 U.S. at 30-31, 101 S.Ct. at 965 (footnote omitted). Thus, even though the opportunity to earn incentive gain time is dependent on the grace of the legislature and the availability of jobs, we conclude that if the State affords its inmates such work, it is bound to reward prisoners for their services at a gain time rate at least equally advantageous to that in effect at the time of those prisoners’ offenses.
¶263.
¶27In a third attempt to distinguish between basic and incentive gain time, the State notes that once the department has determined, in its discretion, that a prisoner has performed his duties in a satisfactory manner, the department has no discretion as to the amount of basic gain time merited by the performance of those duties.10 With regard to incentive gain time, however, the State notes that the department has discretion to determine both whether the prisoner has performed his duties in a diligent or exceptional manner and the amount of incentive gain time that the prisoner’s performance merits. Relying on this distinction, the State argues that since the petitioner may never perform his duties in a manner that would make him eligible for the greater amount of incentive gain time previously available under the 1978 act, any disadvantage to the petitioner is too speculative to constitute a violation of the ex post facto clause.
¶28We agree that a prisoner may be less likely to earn incentive gain time than basic gain time.11 Under Weaver, however, we are not to speculate as to whether an individual prisoner’s future behavior will result in an increased term of incarceration under the new gain time provision. Instead, the decision requires us to examine whether a prisoner is “disadvantaged by the reduced opportunity to shorten his time in prison.” Id. at 33-34, 101 S.Ct. at 967 (emphasis added). Thus, even though, in fact, petitioner may not so diligently perform his assigned duties as to earn the full thirty-seven days of incentive gain time previously available under the 1978 act, the elimination of the opportunity to do so is sufficient to make the 1983 act ex post facto as applied to petitioner.
¶30As its second argument, the State contends that the 1983 act does not violate the Constitution’s prohibition against ex post facto laws because the 1983 provision does not disadvantage the petitioner when compared in toto with the 1978 act.12 Specifically, the State argues that the increased allotment of basic gain time available under the 1983 act compensates for any reduction in the amount of incentive gain time previously available under the 1978 act.13 We disagree.
¶31We recognize that an inmate who performs his duties in only an adequate manner may be better off under the 1983 act— such a prisoner will receive more basic gain time, and is not injured by the elimination of incentive gain time previously awarded only for diligent or outstanding job performance. For purposes of our ex post facto analysis in this case, however, this fact is irrelevant.14 Under Weaver, we need not conclude that a new law disadvantages every prisoner or the average prisoner; instead, our analysis centers on whether the new law disadvantages the particular prisoner who is now before the court. See Weaver, 450 U.S. at 33-34, 101 S.Ct. 966-67.
¶32Comparing the 1983 act in toto with the 1978 act, we note that under the 1983 act petitioner loses the opportunity to earn seventeen extra days of incentive gain time, in exchange for which he receives one extra day of basic gain time.15 As a result, petitioner’s tentative release date under the 1978 act is more than one and one-half years earlier than under the 1983 act. Giv*1502en this information, we have no doubt that the 1983 act is more onerous than the 1978 act.
¶33C.
¶34In its third challenge, the State maintains that in passing the 1978 act, the Florida legislature allowed inmates an increased amount of discretionary gain time in order to offset the reductions in automatic gain time effected by the act. The Supreme Court having found this offset unconstitutional as applied to prisoners convicted of offenses occurring before the act’s passage, the State contends that the Florida legislature now should be entitled to withdraw these increased benefits. This argument is frivolous. Although we recognize that Florida might not have enacted the 1978 statute had the legislature known that the law would be ex post facto as applied to pre-1978 offenders, the Florida legislature did, in fact, enact these provisions. The federal courts recognize no doctrine of “constitutional mistake” that can absolve a legislature from the consequences of a misapprehension concerning a statute’s constitutionality. Thus, the fact that the Florida legislature did not realize that the 1978 act would be ex post facto by no means prevented the rights guaranteed by the 1978 act from vesting in individuals sentenced for offenses committed after the statute’s effective date.
¶35III.
¶36In sum, we conclude that the provisions of Fla.Stat. § 944.275 (1987) that allow prisoners to earn only twenty days per month of incentive gain time constitute an unconstitutional ex post facto law as applied to petitioner.16 The district court’s decision granting petitioner a writ of habeas corpus is therefore
¶37AFFIRMED.