Two insurers issued separate policies, each purporting to insure the same property against loss by fire, each with a loss payable clause in favor of the same institutional mortgagee of the property. Each policy contained a clause providing that it would not be effective if there were other insurance on the property. When the property was damaged by fire, each insurer denied liability under its policy and one contended alternatively that the loss should be prorated. After a bench trial, the district *400judge concluded that, under Mississippi law, which applies in this diversity case,1 both of the policies were in effect and prorated the liability. Concluding that only one of them, the Allstate renewal policy, was in effect when the fire occurred, we reverse in part and affirm in part.

I

In January 1973 Allstate Insurance Company (“Allstate”) issued its Policy No. 190 in the amount of $50,000 insuring property owned by Carroll Ed Sanders in Iuka, Mississippi, and naming Tri-State Savings and Loan Association (“Tri-State”) as mortgagee. The term of this policy extended to January 9, 1976. In August 1974 Allstate issued Policy No. 899 covering both the mortgaged property, at 126 Pearl Street, and other properties owned by'Sanders, and again naming Tri-State as mortgagee. Allstate intended that this policy replace its Policy No. 190, but it failed to cancel the earlier policy, so there were two Allstate policies ostensibly covering the same property at the same time.2 In March 1975 Allstate mailed Tri-State a notice canceling Policy No. 899 for nonpayment of premiums. About the same time it received this notice, Tri-State received a contradictory notice from Allstate dated “January 10,” without mention of the year, stating that Policy No. 899 was to be continued in force without interruption.

In a routine check, A. W. Bonds, the managing officer of Tri-State, reviewed his files in August 1975 to ensure that there was adequate insurance on the Pearl Street property. He could not satisfy himself from the files that there was adequate insurance and he did not receive a satisfactory explanation from Allstate’s Iuka agent. Therefore, to protect Tri-State’s interest, Bonds obtained two consecutive thirty-day binders from Highlands Insurance Company (“Highlands”) through Highlands’ local agent. Highlands’ agent understood that the coverage was temporary, pending determination whether the Allstate policy was effective.

Bonds later concluded that Allstate was not insuring the Pearl Street property. Accordingly, at his request, Highlands issued a policy covering the Pearl Street property in the amount of $35,000, with a loss payable clause in favor of Tri-State as mortgagee. The policy term was September 9, 1975, to September 9, 1978. The district court found that this policy was issued on the basis of Bonds’ assertion that “no other insurance existed on the property.”

Several months later, Allstate issued a new policy, again identified as “No. 190” (“the Allstate renewal policy”), insuring the Pearl Street property for $50,000 from January 9, 1976, to January 9, 1979. This policy also contained a loss payable clause in favor of Tri-State. No application had been made for the policy by either Sanders or Tri-State and no premium was ever paid for it.

The Pearl Street property was destroyed by fire on January 16, 1977. At that time Tri-State had in its files both the Highlands policy and the Allstate renewal policy. TriState later foreclosed on its mortgage but is still due a balance of $33,278.67.

Highlands filed suit against both Allstate and Tri-State seeking a declaratory judgment that its policy was not in effect at the time of the loss. Highlands contends that, because Tri-State violated the “other insurance” clause in Highlands’ policy, it is not liable to Tri-State for any loss caused by the fire. Alternatively, Highlands contends that any liability should be prorated according to the total amount of insurance cover*401age in effect at the time of the loss. State, of course, seeks to recover from both insurers, or either one. Allstate denies liability to Tri-State on the ground that its renewal policy was issued by mistake. Allstate argues in the alternative that the “other insurance” clause in its renewal policy was violated. Tri-

II

Allstate contends that Policy No. 190 was properly terminated in 1975, and the Allstate renewal policy was sent to Tri-State in 1976 through its own clerical error. It contends, therefore, that the renewal policy was not a valid contract of insurance. The district court concluded that Allstate’s renewal policy was in effect when the fire occurred and that Allstate had waived its right to cancel the policy. Allstate challenges both conclusions as misapplications of Mississippi law.

Mississippi law does not allow a party to avoid a contract on the ground of unilateral mistake if the mistake was merely the result of that party’s inattention or negligence. Hunt v. Davis, 208 Miss. 710, 724, 45 So.2d 350, 352 (1950) (quoting Wall v. Wall, 177 Miss. 743, 748, 171 So. 675, 677 (1937)); Sacred Heart S. Missions, Inc. v. Terminix Int’l, Inc., 479 F.Supp. 348, 350-51 (N.D.Miss. 1979). This rule, however, is not inexorable. See Mississippi State Bldg. Comm’n v. Becknell Constr., Inc., 329 So.2d 57, 60-61 (Miss. 1976) (quoting State Highway Comm’n v. State Constr. Co., 203 Or. 414, 435, 436, 280 P.2d 370, 380, 381 (1955)); Sacred Heart S. Missions, Inc. v. Terminix Int’l, Inc., 479 F.Supp. at 351. If (1) the alleged mistake, although unilateral, is of so fundamental a character that the minds of the parties never in fact met, or an unconscionable advantage has been gained; and (2) there was no gross negligence or willful neglect by the party responsible for the mistake, either in committing the mistake or in not seeking relief from it, then the court may, in its discretion, excuse the responsible party. Mississippi State Bldg. Comm’n v. Becknell Constr., Inc., 329 So.2d at 59-60.3

The district judge concluded that Allstate’s business practices precluded it from denying coverage under its renewal policy. As he noted in his findings of fact, Allstate had issued Policy No. 899 to replace Policy No. 190, but, because of clerical error, nevertheless neglected for six months to terminate Policy No. 190. Thus Allstate itself violated the “other insurance” clauses of both Policy No. 190 and Policy No. 8994 by keeping both policies in force simultaneously. Allstate then sent Tri-State conflicting notices, one of them saying Policy No. 899 was canceled, the other saying that policy was to be continued. It further confused matters by failing to provide a full date in the continuation notice. When TriState’s general manager communicated with Allstate to find out whether Allstate had insurance on the Pearl Street property, Allstate was unable to give him a definite answer. Several months later, apparently through another clerical mistake, Allstate sent the renewal policy to Tri-State. Although no one paid the premium on this policy, Allstate allowed the policy to remain in Tri-State’s files for almost a year, with a copy in its own files, and did nothing either to collect the premium or to cancel the policy until after the loss. These findings are sufficient to warrant the district court’s conclusion that Allstate was so negligent that it should not be permitted to invoke its alleged clerical mistake to avoid its contract of insurance with Tri-State on the renewal policy. See Terre Haute Cooperage, Inc. v. Branscome, 203 Miss. 493, 502, 35 So.2d 537, 541 (1948).5

*402Neither assent to coverage nor express acceptance was required of Tri-State. Considering its status as mortgagee, its acceptance of the contract may be implied from its retention of the renewal policy. A mortgagee is not required to mail express acceptance to every insurer who issues a policy protecting its insurable interest or run the risk of noncoverage. We agree with the district court’s conclusion that, in the circumstances of this case, Tri-State’s mere retention of the renewal policy was sufficient to constitute acceptance of a contract of insurance with Allstate.6

This result is not altered by nonpayment of the policy premium. The Allstate renewal policy had a deferred premium payment endorsement that apparently eliminated payment of the premium as a condition precedent to the formation of a valid contract of insurance.7 The record also suggests that Allstate sometimes issued policies and kept them in force even though premiums were not paid on them.8 Moreover, the loss payable provision entitles TriState by law to the benefit of the Mississippi “union” or “standard mortgage clause.” Miss. Code Ann. § 83-13-9.9 This clause *403automatically becomes a part of a fire insurance policy insuring property on which there is a mortgage when the policy contains a loss payable clause for a mortgagee.10 In effect the statutory clause creates a new and independent contract between the mortgagee and the insurer,11 a contract “ ‘dependent for its validity solely upon the course of action of the insurance company and the mortgagee.’ ” Bacot v. Phoenix Ins. Co., 96 Miss. 223, 247, 50 So. 729, 734 (1909) (quoting Syndicate Ins. Co. v. Bohn, 65 F. 165, 178 (8th Cir. 1894)).12 Without ten days’ notice to Tri-State, as loss payee under the Allstate renewal policy, the nonpayment of the premium on the renewal policy could not terminate Tri-State’s coverage.13 National Sec. Fire & Cas. Co. v. Mid-State Homes, Inc., 370 So.2d 1351, 1354 (Miss. 1979).

Allstate concedes that nonpayment of the premium is not dispositive, but relies on it as evidence that Tri-State never assented to the contract of insurance with Allstate proposed by the renewal policy. This argument lacks merit. As mortgagee, Tri-State was only secondarily liable for payment of the premium on this policy. Id.; Hennessey v. Helgason, 168 Miss. 834, 837, 151 So. 724, 725 (1934). Because Allstate never made any demand for payment on Tri-State,14 Tri-State’s nonpayment does not imply rejection, or nonacceptance, of coverage.

Allstate may not escape coverage on the ground that the Highlands policy violated the other insurance clause in the Allstate renewal policy. An insured who violates this clause forfeits his insurance coverage. See Zepponi v. Home Ins. Co., 248 Miss. 828, 833, 161 So.2d 524, 526 (1964). However, “[cjourts frown on forfeitures and lean toward waiver in insurance cases. . . . Forfeitures are not favored if there are any circumstances indicating a waiver thereof.” 16B J. Appleman & J. Appleman, Insurance Law and Practice § 9082, at 506-07 (rev. ed. 1981) (footnote omitted); accord, e.g., Jones v. New York Guar. & Indem. Co., 101 U.S. 622, 628, 25 L.Ed. 1030, 1035 (1880); Travelers Protective Ass’n of Am. v. Jones, *40491 F.2d 377, 378 (5th Cir. 1937). “[Wjhere doubt exists forfeiture will be avoided.” Aetna Ins. Co. v. Jeremiah, 187 F.2d 95, 98 (10th Cir. 1951).

A waiver is a voluntary and intentional relinquishment of a known right15 or conduct that warrants an inference of such a relinquishment.16 Waiver is usually a question of fact to be determined by the jury or, in a bench trial, by the court.17 When the facts are undisputed, however, waiver is a question of law.18 Even “slight circumstances” will support a finding that an insurer has waived a forfeiture clause in an insurance policy,19 for “courts liberally construe in favor of an insured acts or circumstances by the insurer indicating an intention to waive a forfeiture.” 20 Under Mississippi law an insurer may waive its right to forfeit or rescind an insurance policy by continuing the policy in force after learning of facts that would permit it to avoid the policy. Casualty Reciprocal Exch. v. Wooley, 217 So.2d 632, 636 (Miss. 1969).

No one made any misrepresentations to Allstate about the existence of Policy No. 190.21 Because Allstate intended to replace Policy No. 190 with Policy No. 899, “there [was] some circumstance to direct its attention to” the existence and contents of the Policy No. 190 file. Violin v. Fireman’s Fund Ins. Co., 81 Nev. 456, 461, 406 P.2d 287, 290 (1965). Thus the district court could properly have found that Allstate had at least constructive knowledge of the contents of that file when it issued Policy No. 899.22 This constructive knowledge23 is *405enough to support the district court’s conclusion that, by issuing Policy No. 899 and then keeping Policy No. 190 in force for six months, Allstate was deemed to have relinquished its right to enforce the other insurance clause in Policy No. 190 and the renewal policy. See Aetna Ins. Co. v. Smith, McKinnon & Son, 117 Miss. 327, 78 So. 289 (1918); New Orleans Ins. Ass’n v. Holberg, 64 Miss. 51, 8 So. 175 (1886); Hicks v. Home Sec. Life Ins. Co., 226 N.C. 614, 617, 39 S.E.2d 914, 916 (1946) (citing cases); Lanigan v. Prudential Ins. Co., 63 Hun 408,-, 18 N.Y.S. 287, 289-90 (Sup.Ct. 1892).24 Allstate’s carelessness or neglect may not avoid the waiver.25

We conclude, therefore, that the Allstate renewal policy was in effect on the date of the fire.

Ill

Each policy contains a clause prohibiting other insurance. The clause in the Highlands policy reads:

[OJther insurance is prohibited unless the total amount of insurance, including the amount of this policy, is inserted in the blanks provided on the first page of this policy under the caption Total Insurance. This Company shall not be liable for loss while the insured shall have any other insurance prohibited by this policy.26

As we noted earlier, slip op. p. 123, pp. 403-404 supra, violation of this clause voids the policy. It, therefore, provides a defense to a suit for loss occurring while there is additional insurance in violation of the terms of the policy. Zepponi v. Home Ins. Co., 248 Miss, at 833, 161 So.2d at 526; Flowers v. American Ins. Co., 223 Miss. 732, 78 So.2d 886 (1955).

To avoid violating this clause, TriState, upon receiving the Allstate renewal policy, should have disclaimed any interest in the Allstate policy and disclosed its existence to Highlands. See Insurance Co. v. Fitzgerald, 164 Miss. 279, 282, 144 So. 684, 685-86 (1932); National Union Fire Ins. Co. v. Provine, 148 Miss. 659, 670, 114 So. 730, 732 (1927) (“on discovery of the additional insurance, the insured is bound to disclose its existence to his insurer, and unequivocally disclaim any benefits therefrom”).27 Instead, as discussed earlier, Tri-State accepted and retained the Allstate renewal policy in its files along with the Highlands policy. Its acceptance of the Allstate coverage violated the other insurance clause and freed Highlands of any liability to TriState.

Tri-State’s professed ignorance of the existence of the Allstate renewal policy is unavailing, for Tri-State is deemed to have *406knowledge of both the existence and the terms of the insurance policies in its possession. Springfield Fire & Marine Ins. Co. v. Nix, 162 Miss. 669, 673, 138 So. 598, 599 (1932); Home Mut. Fire Ins. Co. v. Pittman, 111 Miss. 420, 423, 71 So. 739, 740 (1916).28 Tri-State had not relied on Sanders to obtain insurance coverage but had itself acted to secure the Highlands policy because it thought it had no coverage. It was not an unwitting victim of manipulation by its debtor. The course of events signaled the Iuka property for its special attention. TriState’s professed good faith in dealing with the two insurers is irrelevant. “If the additional insurance clause is violated, the good faith or bad faith of the insured in breaching the clause is wholly immaterial.” National Union Fire Ins. Co. v. Provine, 148 Miss. at 670, 114 So. at 732, quoted in Prissock v. Western Fire Ins. Co., 360 F.Supp. 1346, 1348 (N.D.Miss. 1973).29

Tri-State cannot invoke the provision of Miss. Code Ann. § 83-13-9 that requires an insurer to give a mortgagee ten days’ notice of cancellation of an insurance policy in which the mortgagee is a loss payee. That provision protects the mortgagee from loss occurring after the mortgagor or owner of an insured property causes a lapse in insurance coverage.30 In this case, however, Tri-State itself violated the other insurance provision and caused the Highlands policy to be voided. Tri-State must suffer the consequences of its own acts or omissions under its policy with Highlands.

Moreover, Highlands had no previous notice, actual or constructive, of the existence of other insurance on the Pearl Street property. Highlands issued its policy in reliance on the representation that there was no other insurance on the property. It did not learn of the other insurance until after the fire. At that point, a ten day cancellation notice would have served no purpose, for “the rights of the parties had become fixed by the burning of the property.” Insurance Co. v. Fitzgerald, 164 Miss, at 282, 144 So. at 685.

For these reasons, we conclude that TriState violated the other insurance clause in the Highlands policy and thereby freed Highlands of its obligations under its policy with Tri-State.

IV

The judgment against Allstate is AFFIRMED and MODIFIED. Judgment shall be entered against Allstate for $33,278.67, the full amount due Tri-State. The judgment against Highlands is REVERSED and judgment shall be entered in its favor declaring it not liable for any part of TriState’s loss.