All warrants for payment of any indebtedness of a rural fire protection district which are unpaid for want of funds shall bear interest at a rate specified by the issuing district and endorsed on the warrant, from the date of the registering of such unpaid warrants with the county treasurer; Provided, that the amount of such warrants does not exceed the revenue provided for the year in which the indebtedness was incurred.
Neb. Rev. Stat. §§ 35-512