diff --git a/src/vehicle_gui.cpp b/src/vehicle_gui.cpp
--- a/src/vehicle_gui.cpp
+++ b/src/vehicle_gui.cpp
@@ -377,6 +377,7 @@ static void VehicleRefitWndProc(Window *
 							int command = 0;
 
 							switch (v->type) {
+								default: NOT_REACHED();
 								case VEH_TRAIN:    command = CMD_REFIT_RAIL_VEHICLE | CMD_MSG(STR_RAIL_CAN_T_REFIT_VEHICLE);  break;
 								case VEH_ROAD:     command = CMD_REFIT_ROAD_VEH     | CMD_MSG(STR_REFIT_ROAD_VEHICLE_CAN_T);  break;
 								case VEH_SHIP:     command = CMD_REFIT_SHIP         | CMD_MSG(STR_9841_CAN_T_REFIT_SHIP);     break;