Mo. Rev. Stat. § 389.870

Any employee of such railroad so operated as aforesaid who may be injured by any train, locomotive, tender, car or similar vehicle in use contrary to the provisions of sections 389.810 to 389.870 shall not be deemed to have assumed the risk thereby occasioned, nor to have been guilty of contributory negligence, because of continuing in the employment of such railroad or in the performance of his duties as such employee after the unlawful use of such train, locomotive, tender, car or similar device shall have been brought to his knowledge.