Opinion by
Me. Chief Justice Jones,Pursuant to the October 28, 1971, order of the United States District Court for the Eastern District of Pennsylvania at Criminal Action No. 71-1811, appellant was resentenced on a 1965 second-degree murder conviction by the Court of Quarter Sessions of Chester County on December 10, 1971.1 At that time, a sentence of eight and one-half to ten years was imposed and appellant was returned to prison with a commitment order for the same duration. Three days later, the court amended this sentence, increasing the maximum term to twenty years, thus making the sentence eight and one-half to twenty years. This appeal is from that order.
Appellant asserts that the lower court’s action in raising his maximum sentence constituted double jeopardy and thus violated the Fifth Amendment to the United States Constitution and Article I, Section 10 of the Pennsylvania Constitution. The Commonwealth, however, contends that the imposition of the longer maximum sentence merely corrected a prior “slip of *276the tongue” of the sentencing judge and was therefore permissible. In support of this factual theory, the Commonwealth points to several convincing factors.2 Nevertheless, for the reasons given below and particularly in view of our decision in Commonwealth v. Allen, 443 Pa. 96, 277 A. 2d 803 (1971), we are of the view that the sentencing judge’s inadvertence is of no aid to the Commonwealth and that the increased sentence was unlawful as being violative of double jeopardy.
The United States Supreme Court has held that neither the guarantee against double jeopardy nor the equal protection clause bars a more severe sentence upon reconviction following an accused’s successful appeal. North Carolina v. Pearce, 395 U.S. 711, 723 (1969). However, Pearce also holds that “[d]ue process . . . requires that vindictiveness against a defendant for having successfully attacked his first conviction must play no part in the sentence he receives after a new trial.” 395 U.S. at 725. Therefore any time a more severe sentence is imposed on a defendant, it must be justified by intervening conduct by the defendant occurring after the date of the original sentence. 395 U.S. at 726.
The present problem deals with the increase of an existing sentence,3 not with an increase over the original sentence following retrial as was the case in *277Pearce. That distinction, however, is not significant here since both the United States Supreme Court and this Court have also held that a court is without power to increase an existing sentence, once the defendant has begun to serve that sentence. See Ex parte Lange, 85 U.S. (18 Wall.) 163 (1873); Commonwealth v. Silverman, 442 Pa. 211, 275 A. 2d 308 (1971).
More important for our resolution of the instant case, however, is our decision in Commonwealth v. Allen, supra, wherein we held, inter alia, that even an increase in sentence which is merely designed to correct an inadvertent judicial mistake must be scrutinized as carefully as an increase which results from a reconsideration of sentencing factors or from a judicial change of mind.4 The Commonwealth would dispute this reading of Allen, however, since it feels that an increased sentence to correct a “slip of the tongue” was there approved. While it is true that we noted factors which negated a “slip of the tongue” theory in that case,5 we never indicated that the establishment of such a “slip” would have altered our result. On the contrary, we there expressed our “agreement with those jurisdictions holding there is no exception to Lange in the situation where the increase is allegedly designed to reflect the judge’s true intent. . . .” 443 Pa. at 104, 277 A. 2d at 807.6 We then concluded our discussion *278with the following language: “Lastly, we are of the opinion that such alleged inadvertence cannot be tolerated as a matter of public policy. As best stated by the Second Circuit, £[t]he possibility of abuses inherent in broad judicial power to increase sentences outweighs the possibility of windfalls to a few prisoners.’ 367 F. 2d at 370.” 443 Pa. at 105, 277 A. 2d at 807. In light of the above principles enunciated in Allen, we must hold that the modification of sentence in the present case, having occurred after the appellant was returned to prison pursuant to a commitment order, violated the federal and state constitutional guarantees against double jeopardy.
There is, however, one more problem. As was noted in the opinion of the court below, the eight and one-half to ten year sentence initially imposed after the federal court order is unlawful since the minimum is greater than one-half the maximum. Act of September 26, 1951, P. L. 1460, §1, 19 P.S. §1057. The method of correcting this illegality, however, is not to increase the maximum until the sentence comports with the statute as did the lower court in this case; rather, in light of our foregoing discussion, the appropriate action must be to reduce the minimum term until there is statutory compliance and under no circumstances to increase either minimum or maximum term. Hence, a five to ten year sentence is the most severe punishment which can be imposed on appellant at this time.
Accordingly, the order of the Court of Quarter Sessions of Chester County is reversed, the judgment of sentence is vacated, and the case remanded for resentencing in accordance with this opinion.
The basis for the District Court’s order of resentencing was its finding that the Chester County court had considered a subsequently voided 1956 conviction in imposing a ten to twenty year sentence on the 1965 conviction.
Apparently, prior to the initial resentencing, there was a conference in chambers in which the sentencing .iudge indicated that he was going to impose an eight and one-half to twenty year sentence. The Commonwealth also stressed the promptness with which the sentence was changed (three days) and the illegality of the sentence as originally imposed (eight and one-half to ten) since the minimum sentence cannot exceed one-half the maximum See Act of September 26, 1951, P. L. 1460, §1, 19 P.S. §1057.
There was, of course, an original sentence in this case, but that fact is irrelevant to our present discussion as we are here concerned only with those events which occurred subsequent to the resentencing order of the federal district court
Although there was some hint of possible exceptions where, for example, (1) the original sentence was below the minimum mandatory sentence and the mistake is cured within a few hours and (2) where the mistake was due to a clerk’s erroneous docket entry, the thrust of that opinion indicated that a prophylactic rule would be more desirable. 443 Pa. at 104-05, 277 A. 2d at 806-07.
443 Pa. at 104, 277 A. 2d at 806.
The Lange case, which we cited in Allen, held that once a defendant is sentenced by the court and has commenced to serve that sentence, the court is without power to increase that sentence, even during that term of court. Ew parte Lange, 85 U.S. (18 Wall.) 163 (1873).