Okla. Stat. tit. 60, § 181

Any trust of a trustor dying after December 31, 1981, which contains a marital deduction formula expressly providing that the spouse of the trustor is to receive the maximum amount of property qualifying for the marital deduction allowable by federal law shall be construed as referring to the unlimited marital deduction provided by the Economic Recovery Tax Act of 1981, Public Law 97-34. This provision shall apply retrospectively to trusts of trustors dying after December 31, 1981.