Mo. Rev. Stat. § 431.183: Payment contingent upon payment from third party, not a defense to enforcement of lien.

Any provision in a contract, agreement or understanding that provides that a payment from a contractor to a subcontractor, trade contractor, specialty contractor or supplier is contingent or conditioned upon receipt of a payment from any other private party, including a private owner, is no defense to a claim to enforce a mechanic's lien pursuant to the provisions of chapter 429.