Mo. Rev. Stat. § 537.210: Contracts limiting liability invalid.

No contracts made between any railroad corporation, or between any person, company or corporation operating a mine or mines and their agents or servants, based upon the contingency of the injury or death to any such agent or servant, limiting the liability of the employer for any damages under the provisions of this and sections 537.180 to 537.200 shall be valid or binding, but all such contracts or agreements shall be null and void.