Mo. Rev. Stat. § 513.485: Proceedings where encumbered by mortgage.

If, at the time of such levy of execution, the homestead or real estate mentioned in section 513.480 shall be encumbered by mortgage, the value and location of such homestead shall be fixed as provided in said section, and thereupon such levy shall proceed in the same manner as in the case of mortgages existing upon distinct parcels of land.