A dependent child of a wage earner is entitled to “child’s insurance benefits” under the Social Security Act if the wage earner is insured under the Act and dies, becomes disabled, or reaches the age of 65. 42 U.S.C. § 402(d). Problems of determining entitlement sometimes arise when the .wage earner dies and was not married to the child’s mother. The Act contains an exhaustive list of methods of establishing entitlement to child insurance benefits in such a case: proof that the wage earner would have been married to the child’s mother but for a technical deficiency in the marriage; a written acknowledgment of paternity by the wage earner; a judicial decree that the wage earner was the child’s father, provided the decree was issued before the wage earner died; a court order that the wage earner contribute to the support of the child because the wage earner was the child’s parent; a determination by the Social Security Administration that the wage earner was the parent of the child and was living with or contributing to the support of the child when the wage earner died; or proof that the child was entitled to inherit from the wage earner under the law of intestate succession of the wage earner’s state of domicile. 42 U.S.C. §§ 416(h)(1)(B), (2), (3). Only the last-mentioned of these methods (§ 416(h)(2)(A)) was available to Scott M. Glenn, II, the applicant in our case, born November 6, 1992, eight months after the death in an automobile accident of Scott M. Glenn, the wage earner. The child’s mother, Christi Haas, had not been married to the wage earner or living with him; no paternity decree or support order had been issued; and he had provided no support directly or indirectly to the unborn child.
*561One month after Scott’s birth, his mother filed a petition in an Indiana state court to establish the wage earner’s paternity. The wage earner’s mother, who was the personal representative of his estate, testified in support of paternity, and the court entered a declaration that the wage earner was indeed the child’s father. The estate later filed a suit for wrongful death based on the accident in which the wage earner had been Mlled. The court in which that suit was filed determined that the child, as the only dependent next of kin of a decedent who had left no widow, was entitled to the proceeds of the suit (which was eventually settled). Ind. Code § 34-1-1-2.
The administrative law judge acknowledged that there was satisfactory evidence of the wage earner’s paternity but nevertheless denied the application for benefits. Young Glenn’s eligibility for benefits depended on his eligibility to inherit under Indiana’s intestate succession law, and Ind.Code § 29-1-2-7(b) provides that, “for inheritance,” a child bom out of wedlock will be treated as if his parents were married only if
(1) The paternity of the child has been established by law in a cause of action that is filed:
(A) During the father’s lifetime; or
(B) Within five (5) months after the father’s death; or
(2) The putative father marries the mother of the child and acknowledges the child to be his own. [Emphasis added]
The suit to establish the wage earner’s paternity “for inheritance” had been brought one month after the child’s birth and therefore nine months after the wage earner’s death: too late.
The appellant argues that the five-month statutory deadline is merely a statute of limitations and hence is waived by not being pleaded. It was not pleaded in the paternity suit. In fact that suit was uncontested. The most common type of paternity suit is one brought against a man who denies paternity, or at least doesn’t want the financial burdens of fatherhood. Here the man was dead, and apparently left no assets other than a claim for wrongful death. Since the personal representative of his estate believed herself to be the child’s grandmother, and since unless she herself had been dependent on the decedent, of which there is no hint in the record, she would have had no personal stake in the wrongful-death action, she had no financial incentive to resist the paternity suit and she did not resist it. She had nothing to lose and money for the child whom she believed to be her grandson to gain.
Although the facts are unusual and doubts about the wage earner’s paternity slight, the danger of collusive paternity suits is not slight. Whenever the putative father dies, a child or children can sue to establish paternity, knowing that the father’s estate, if it has no assets or at least no assets other than what a child might claim, may not bother to contest the suit. In such a case a spurious allegation of paternity might provide the basis for awards of child insurance benefits, for certain life insurance or employee death benefits, for the inheritance of an intestate estate that might otherwise escheat to the state because the decedent had no known relatives, or for the proceeds of a legal judgment. The first and last incentives for a collusive paternity suit were present here and the suit was not contested, although, as we said, the probability seems slight that the allegation of paternity was spurious. We do not know, of course. We have pointed out that the grandmother had no stake in the wrongful-death suit and therefore no reason to resist the claim of paternity; nor did anyone else. But we do not rest our decision on any doubts that Glenn senior is the claimant’s father.
Whether Indiana’s five-month statute of limitations was motivated by a concern with preventing collusive paternity suits, or whether, as suggested in S.V. v. Estate of Bellamy, 579 N.E.2d 144, 148 (Ind.App.1991), the only concern was with the prompt winding up of estates (for remember that the five-month limitation is applicable only when the purpose of the paternity suit is to establish a right of inheritance), the policy behind the deadline would be impaired were the deadline deemed waived simply by not being pleaded. This makes it unlikely that the Indiana legislature intended the deadline to be an ordinary statute of limitations, which *562like other affirmative defenses is waived if the defendant fails to plead it. Its location in the statute is another clue that it is an element of the plaintiffs claim rather than an affirmative defense. Bocek v. Inter-Insurance Exchange, 175 Ind.App. 69, 369 N.E.2d 1093, 1097 (1977); General Motors Corp. v. Arnett, 418 N.E.2d 546, 548 (Ind.App.1981). The distinction between the two types of limitation is a familiar one in the law, Boggs v. Adams, 45 F.3d 1056, 1060 and n. 8 (7th Cir.1995), though it has been criticized as archaic. Tregenza v. Great American Communications Co., 12 F.3d 717, 719 (7th Cir.1993).
It is true that Indiana courts have sometimes construed deadlines for bringing paternity suits as mere statutes of limitations. In re Paternity of T.C.S., 576 N.E.2d 633 (Ind.App.1991); D.E.F. v. E.M., 173 Ind.App. 274, 363 N.E.2d 1030, 1032 (1977). But these were not cases in which the objective of the suit was to establish entitlement to inherit. Such a suit is governed by the five-month limitation, which if waivable would expose the settlement of decedents’ estates to debilitating uncertainty. A new heir might appear, claiming a share of the estate, after the assets of the estate had been distributed to the known heirs, and the defendant in the paternity suit might fail, deliberately or inadvertently, to plead the statute of limitations. That is not an issue here, but we are considering whether the deadline would be waiva-ble in suits brought under the Indiana statute, that is, suits to establish paternity for the purpose of inheritance. Bocek holds that time limits on the bringing of suits based on statutory rights are elements of the claim, and neither T.C.S. nor D.E.F. alludes to this principle; maybe it was not argued in those cases. Bocek does not stand alone. Two other Indiana cases hold that the identical five-month deadline for bringing suit against a decedent’s estate is an element of the claim and not merely a statute of limitations. McEwen v. McEwen, 529 N.E.2d 355, 358-59 (Ind.App.1988); Rising Sun State Bank v. Fessler, 400 N.E.2d 1164, 1166 (Ind.App.1980). The statutory language at issue in those cases was more emphatic than the statutory language at issue here — it was that suits not brought within five months “shall be forever barred.” Ind.Code § 29-1-14-1(a). But given the identity of the deadlines and the fact that both statutes are concerned with inheritance (and so presumably reflect the same desire for a swift resolution of decedents’ estates), we would be surprised to find the deadline treated as an element of the claim in one and as a mere statute of limitations in the other. An argument could be made that the deadline should be tolled until the child was born, but Haas does not make the argument, perhaps because it was considered and rejected in S.V. v. Estate of Bellamy, supra, 579 N.E.2d at 145.
We add for completeness that even if the five-month deadline is waivable, the Social Security Administration might not be bound by a determination of paternity made in an uncontested proceeding. George v. Sullivan, 909 F.2d 857 (6th Cir.1990); Gray v. Richardson, 474 F.2d 1370, 1373 (6th Cir.1973). But the Social Security Administration did not base its denial of benefits on the lack of contest, so neither may we. We are convinced that the five-month deadline is non-waivable.
This short, unwaivable deadline is a crude device for discouraging fraudulent or collusive paternity claims designed to establish a right of inheritance; but it is not completely arbitrary. When the unmarried father of a child dies, and there has been no determination of paternity, almost the mother’s first concern will be the establishment of paternity and she can be expected therefore to move immediately. If she does not, this may be an indication that she does not believe, or at least lacks confidence, that the “father” really is her child’s father. Granted, it is a weak indication. It might not occur even to a person relatively knowledgeable about law that a paternity suit could be, let alone that it must be, brought before the birth of the child whose paternity was to be determined. Given this point and the high probability that the wage earner in this ease really is the child’s father, the application of the statute produces a harsh result and thus sets the stage for the appellant’s challenge to the statute’s constitutionality, or more precisely to the constitutionality of the statute’s incorporation into the Social Security Act.
*563The two issues are not identical, and the first is a nonstarter. A child seeking to inherit property from his natural father under Indiana intestacy law might challenge the five-month deadline, arguing that it makes the statute discriminate impermissibly against children bom out of wedlock, in violation of the equal protection clause. But it is pretty certain that the argument, and the suit based upon it, would fail. The interest in protecting decedents’ estates against phony claims and in winding up these estates promptly and definitively has been held to justify even tighter limitations. Lalli v. Lalli, 439 U.S. 259, 99 S.Ct. 518, 58 L.Ed.2d 503 (1978), held constitutional a state statute that required a court order of filiation before the putative father’s death. S.V. v. Estate of Bellamy, supra, 579 N.E.2d at 148-49, upheld Indiana’s five-month limitation against the challenge just sketched, in reliance on Lalli. See also Trammell on behalf of Trammell v. Bowen, 819 F.2d 167, 170 (7th Cir.1987).
Applied to this case, the statute upheld in Lalli would have required the impossible: a court order of filiation within one month of conception. We cannot be certain that Lalli, which involved an adult child seeking to inherit, would have come out the same way had the facts been as in the present case. Several courts have held since Lalli that if state law makes it impossible in the circumstances to establish paternity, the law is unconstitutional if applied in those circumstances. Handley by and through Herron v. Schweiker, 697 F.2d 999, 1004 (11th Cir.1983); Cox v. Schweiker, 684 F.2d 310, 323 (5th Cir.1982). The Fourth Circuit disagrees. Jones v. Schweiker, 668 F.2d 755 (4th Cir.1981), vacated because of a change in state law as Jones v. Heckler, 460 U.S. 1077, 103 S.Ct. 1763, 76 L.Ed.2d 339 (1983); Parsons for Bryant v. Health & Human Services, 762 F.2d 1188, 1190 (4th Cir.1985). So does an Eleventh Circuit decision subsequent to Handley, though it involves a different section of the Social Security Act: Orsini on behalf of Orsini v. Sullivan, 903 F.2d 1393 (11th Cir.1990). In any event, there is no impossibility here; Christi Haas knew that she was pregnant, and she had five months to sue. She must also have known that since she neither had been married to the father nor lived with him, his paternity might be questioned. All she had to do was file the paternity suit within five months of Scott Glenn’s death; the statute does not require that the determination of paternity be made within that (or any other) period. The filing would not be burdensome, and it would provide notice to the estate.
Young Glenn is not seeking a share of his putative father’s estate. He is seeking child insurance benefits that are no part of the estate. So the policy of protecting estates is not in play. Another policy is, however. The purpose of federal child insurance benefits, a purpose shared by some but of course not all bequests, is to replace the support that the child would have received from his father had the father not died. Trammell by Trammell v. Bowen, supra, 819 F.2d at 169. Consistent with this purpose, the sections of the Social Security Act that define the entitlements of children born out of wedlock, 42 U.S.C. §§ 416(h)(2) and (3), have been crafted not to determine paternity alone but paternity plus likelihood of support. Every father whose parental rights have not been terminated (as by the lawful adoption of the child by another person) has a legal duty to support his child, Ind.Code § 35-46-1-5; 1 Homer H. Clark, Jr., The Law of Domestic Relations in the United States § 5.4, p. 317 (2d ed. 1987), but the reality is of course different and many fathers, especially of children born out of wedlock, do not support their children. The fact that Scott M. Glenn, II, is probably the child of the wage earner is not by itself proof or even strong evidence that if Glenn senior had lived he would have supported the child. The Social Security Act establishes criteria designed to identify the likely supporters. The criteria constitute a coarse filter, but not so coarse a one that we are moved to declare the relevant provisions unconstitutional, especially since the appellant’s lawyer has no suggestions for an alternative method of screening out the applications of children whose fathers would not have been likely, had they lived, to support them. It is true that Scott’s “dependency” was determined in the wrongful-death action, but that determination has no standing under *564the Social Security Act, and for all we know may have been based simply on the judgment in the paternity suit.
Although the equal protection clause of the Constitution has been interpreted to forbid unreasonable discrimination against children born out of wedlock, e.g., Weber v. Aetna Casualty & Surety Co., 406 U.S. 164, 92 S.Ct. 1400, 31 L.Ed.2d 768 (1972); see Bennemon on behalf of Williams v. Sullivan, 914 F.2d 987, 988-89 (7th Cir.1990), some difference in treatment is inevitable. The institution of marriage is not purely arbitrary or conventional. One of its advantages— historically one of its most important functions — is to establish a clear framework for the support of children. When the framework is missing, the child is at a disadvantage in establishing a range of entitlements, and one of them is to child insurance benefits under the Social Security Act. With Glenn senior dead, the question what if any support he would have provided to the child of a woman to whom he was not married and with whom he had not been living became inherently uncertain. The fact that he died eight months before the child was born aggravated the uncertainty.
It is true that one of the grounds in the Social Security Act for the award of child insurance benefits is a determination by the Social Security Administration that the wage earner was contributing to the support of the applicant when he died. Financial contributions made by the wage earner to the mother during pregnancy have been construed as support for the as yet unborn child. E.g., Adams v. Weinberger, 521 F.2d 656, 660 (2d Cir.1975); Parsons for Bryant v. Health & Human Services, supra, 762 F.2d at 1191; Doran v. Schweiker, 681 F.2d 605, 609 (9th Cir.1982). How regular and substantial the contributions must be to satisfy the statute remains unsettled, Bennemon on behalf of Williams v. Sullivan, supra, 914 F.2d at 990, but the issue is academic here because Glenn senior contributed nothing to the support of the child’s mother. We have been given no reason to suppose that he intended to marry or live with her, to contribute to her support or that of the child, or even to acknowledge paternity.
Congress has decided that, all other routes to demonstrating the likelihood of support being closed, if the child’s state was willing to allow the child to take by intestacy from the putative father this is enough evidence that the putative father would have supported the child to entitle the child to benefits in lieu of that support taken away by death. Congress may not have been required to go that far. Mathews v. Lucas, 427 U.S. 495, 514-15, 96 S.Ct. 2755, 2766-67, 49 L.Ed.2d 651 (1976), holds that Congress was not required to go further. Mathews upheld section 416(h)(2), the section on which the Social Security Administration relies in this case, against a challenge that it is too crude a predictor that the deceased father, had he lived, would have supported the child. See also Imani on behalf of Hayes v. Heckler, 797 F.2d 508, 513 (7th Cir.1986); Trammell v. Bowen, supra. We are mindful that Daniels on behalf of Daniels v. Sullivan, 979 F.2d 1516, 1521 (11th Cir.1992), holds that the equal protection clause forbids Congress to use a short state-law deadline for establishing paternity for inheritance to block a claim for child insurance benefits, since support and inheritance involve a different balance of interests. The court in Daniels did not explain how its result could be reconciled with Mathews v. Lucas, and its conclusion is in conflict not only with the Fourth Circuit’s decisions in Jones and Parsons but also with the Eleventh Circuit’s own decision in Orsini, as well as with the spirit of our decision in Imani.
Even if section 416(h)(2) is invulnerable to constitutional challenge, we are sure, as the Social Security Administration conceded in Lawrence on behalf of Lawrence v. Chater, - U.S. -, 116 S.Ct. 604, 133 L.Ed.2d 545 (1996) (per curiam), that Congress did not intend the incorporation of unconstitutional state intestacy statutes. If the five-month deadline in the Indiana statute could not constitutionally be applied in a suit by a child to inherit property, then it could not be used as the basis for denying claims under the Social Security Act. Cox v. Schweiker, supra, 684 F.2d at 317-18. But this route, it seems, is blocked by Lalli. The Indiana statute is constitutional.
*565With Lalli having upheld a limitations period for determining heirship that is even shorter than Indiana’s, and Mathews v. Lucas having upheld the incorporation of such limitations into the federal statute, the application for benefits in the present cases is doomed unless the Supreme Court is minded to reexamine either decision or unless the present case can somehow be distinguished from Lalli. Mills v. Habluetzel, 456 U.S. 91, 100, 102 S.Ct. 1549, 71 L.Ed.2d 770 (1982), decided after Lalli held that 12 months after the child’s birth was an unconstitutionally short deadline for a child bom out of wedlock to bring a suit for support against his putative father, and here suit was brought only one month after the child’s birth. See also Pickett v. Brown, 462 U.S. 1, 18, 103 S.Ct. 2199, 2209, 76 L.Ed.2d 372 (1983); Clark v. Jeter, 486 U.S. 456, 464, 108 S.Ct. 1910, 1915-16, 100 L.Ed.2d 465 (1988). Yet none of the opinions in these cases questions the continued validity of Lalli. See, e.g., Mills v. Habluetzel, supra, 456 U.S. at 99, 102 S.Ct. at 1554-55. The eases did not involve claims against an estate, so the policy of winding up estates swiftly was not in the pan on the state’s side of the balance. Of course the present case does not involve a claim against an estate either. But Congress’s policy, expressly upheld in Mathews v. Lucas, is, as we have seen, to tie entitlement to child insurance benefits to entitlement to intestacy benefits, or in other words to make the child’s claim against the Social Security Administration depend upon the outcome of a hypothetical claim against the estate. If the latter would fail, the former fails. The element of arbitrariness has been deemed tolerable.
Lalli is different from this case because, as we pointed out earlier, the claimant there was an adult and had had many years to establish paternity. Similarly, the claimant in Trammell had a number of alternative routes to establishing entitlement to the benefits he sought. Our claimant was in a bind, having not yet been bom when his putative father died. Nevertheless, as there is no question of its having been impossible for the mother to have instituted a paternity suit within five months of the wage earner’s death, we cannot find any adequately clear, minimally predictable basis for carving out an exception to Lalli. We could hold, as urged by the plaintiff, that a five-month deadline for the bringing of paternity suits on behalf of posthumously bom children is unconstitutionally short, even when the object of the suit is to establish a right of inheritance. But then what would be the minimum deadline? Five months after birth? This would give the mother 14 months to sue if the decedent had died immediately after conception, significantly delaying the winding up of estates. The harm from such delay would have to be balanced against the harm to the children. Lalli implies that the balance is for the state to strike within limits not here exceeded.
The combined effect of Lalli and Mathews is to place claimants in the position of young Scott in a box. Lalli makes clear that the Indiana statute is constitutional as applied to inheritance, Mathews that the Social Security Act is constitutional in incorporating the (constitutional) Indiana statute. Only the Supreme Court possesses the key that will open the box. We cannot be certain that it will turn the key. Courts are inclined to leave arbitrary line-drawing to legislatures. The creation of the exception sought by the plaintiff would entail a degree of statutory fine-tuning that may or may not exceed the Supreme Court’s current conception of what the judiciary may properly and feasibly accomplish in the name of the Constitution. That is for the Court, not us, to say.
Affirmed.