Okla. Stat. tit. 84, § 84-143: Gift to witness void - Exception

All beneficial devises, legacies or gifts whatever, made or

given in any will to a subscribing witness thereto, are void unless

there are two other competent subscribing witnesses to the same; but

a mere charge on the estate of the testator for the payment of debts

does not prevent his creditors from being competent witnesses to the

will.