A borrower of money must pay the amount due in such money as is current at the time when the loan becomes due, whether such money is worth more or less than the actual money lent.

Source: CivC 1877, § 1093; CL 1887, § 3716; RCivC 1903, § 1412; RC 1919, § 1035; SDC 1939, § 38.0102.