In such contracts, there shall be a provision that there shall be a period of grace of one month, but not less than thirty days, within which any stipulated payment to the insurer falling due after the first may be made, subject at the option of the insurer, to an interest charge thereon at a rate to be specified in the contract but not exceeding six percent per annum for the number of days of grace elapsing before such payment, during which period of grace, the contract shall continue in full force; but in case a claim arises under the contract on account of death prior to expiration of the period of grace before the overdue payment to the insurer of the deferred payments of the current contract year, if any, are made, the amount of such payments, with interest on any overdue payments, may be deducted from any amount payable under the contract in settlement.