An ice maker includes an upper assembly having an upper tray that defines upper portions of a plurality of ice making chambers. The ice maker also includes a lower assembly that is located vertically below the upper assembly and configured rotate relative to the upper assembly. The lower assembly includes a lower tray that defines lower portions of the plurality of ice making chambers, and a lower support that is configured to receive the lower tray and restrict an outward expansion of the lower portions of the plurality of ice making chambers. The lower tray includes a lower tray body configured to hold a first volume of water, and a circumferential wall that extends upward from the lower tray body and is configured to hold a second volume of water above the first volume of water.