A surgical instrument, comprising: (a) a body assembly that includes at least one electrical connection; (b) an end effector operable to treat tissue including first and second opposing jaws; and (c) a shaft assembly extending between the body assembly and the end effector along a shaft axis, wherein the shaft assembly comprises: a nozzle that includes at least one housing, wherein the at least one housing includes a recess (371, 403), a closure tube configured to rotate relative to the body assembly about the shaft axis, and a fluid blocker disposed within the recess (371, 403) of the nozzle, wherein the fluid blocker is configured to contact the closure tube to prevent fluid from entering the nozzle and reaching the at least one electrical connection disposed within the body assembly, wherein the fluid blocker includes an annular member that entirely surrounds the closure tube and the at least one housing includes first and second proximal housings that collectively form the recess (371, 403) configured to receive the annular member, and characterized in that the annular member includes first and second portions that are completely separable from one another, wherein the first proximal housing of the nozzle captures the first portion of the annular member and the second proximal housing of the nozzle captures the second portion of the annular member. (a) a body assembly that includes at least one electrical connection; (b) an end effector operable to treat tissue including first and second opposing jaws; and (c) a shaft assembly extending between the body assembly and the end effector along a shaft axis, wherein the shaft assembly comprises: a nozzle that includes at least one housing, wherein the at least one housing includes a recess (371, 403), a closure tube configured to rotate relative to the body assembly about the shaft axis, and a fluid blocker disposed within the recess (371, 403) of the nozzle, wherein the fluid blocker is configured to contact the closure tube to prevent fluid from entering the nozzle and reaching the at least one electrical connection disposed within the body assembly, wherein the fluid blocker includes an annular member that entirely surrounds the closure tube and the at least one housing includes first and second proximal housings that collectively form the recess (371, 403) configured to receive the annular member, and characterized in that the annular member includes first and second portions that are completely separable from one another, wherein the first proximal housing of the nozzle captures the first portion of the annular member and the second proximal housing of the nozzle captures the second portion of the annular member. a nozzle that includes at least one housing, wherein the at least one housing includes a recess (371, 403), a closure tube configured to rotate relative to the body assembly about the shaft axis, and a fluid blocker disposed within the recess (371, 403) of the nozzle, wherein the fluid blocker is configured to contact the closure tube to prevent fluid from entering the nozzle and reaching the at least one electrical connection disposed within the body assembly, wherein the fluid blocker includes an annular member that entirely surrounds the closure tube and the at least one housing includes first and second proximal housings that collectively form the recess (371, 403) configured to receive the annular member, and characterized in that the annular member includes first and second portions that are completely separable from one another, wherein the first proximal housing of the nozzle captures the first portion of the annular member and the second proximal housing of the nozzle captures the second portion of the annular member.