Okla. Stat. tit. 12A, § 12A-2A-208: Modification, rescission, and waiver

MODIFICATION, RESCISSION, AND WAIVER

(1) An agreement modifying a lease contract needs no

consideration to be binding.

(2) A signed lease agreement that excludes modification or

rescission except by a signed record may not be otherwise modified

or rescinded, but, except as between merchants, such a requirement

on a form supplied by a merchant must be separately signed by the

other party.

(3) Although an attempt at modification or rescission does not

satisfy the requirements of subsection (2) of this section, it may

operate as a waiver.

(4) A party who has made a waiver affecting an executory

portion of a lease contract may retract the waiver by reasonable

notification received by the other party that strict performance

will be required of any term waived, unless the retraction would be

unjust in view of a material change of position in reliance on the

waiver.