Okla. Stat. tit. 42, § 42-99: Priority of mortgage liens

The lien herein provided for shall be subject to prior mortgage

liens, unless the holder thereof has received notice of the

intention of the furnishing of said labor, money, material or

supplies and consents thereto in writing after which the holder of

such mortgage lien shall become jointly liable with the owner of

said property for the expense of producing, altering or repairing of

same.