Mo. Rev. Stat. § 509.400

All defenses and objections for which there is no provision for the raising of the same by motion shall be raised in the responsive pleading if one is permitted. When no responsive pleading is required the case shall be deemed at issue. If a responsive pleading is required all defenses or objections not raised therein are waived, except failure to state a claim upon which relief can be granted, or failure to state a legal defense to a claim, and, except lack of jurisdiction over the subject matter. All issues of fact raised or deemed to be raised shall be determined at the trial.