diff --git a/players.c b/players.c
--- a/players.c
+++ b/players.c
@@ -710,6 +710,7 @@ int32 CmdReplaceVehicle(int x, int y, ui
 		case 3: {
 			EngineID old_engine_type = GB(p2, 0, 16);
 			EngineID new_engine_type = GB(p2, 16, 16);
+			int32 cost;
 
 			if (new_engine_type != INVALID_ENGINE) {
 				/* First we make sure that it's a valid type the user requested
@@ -729,10 +730,14 @@ int32 CmdReplaceVehicle(int x, int y, ui
 				if (!HASBIT(GetEngine(new_engine_type)->player_avail, _current_player))
 					return CMD_ERROR;
 
-				return AddEngineReplacement(p, old_engine_type, new_engine_type, flags);
+				cost = AddEngineReplacement(p, old_engine_type, new_engine_type, flags);
 			} else {
-				return RemoveEngineReplacement(p, old_engine_type, flags);
+				cost = RemoveEngineReplacement(p, old_engine_type, flags);
 			}
+
+			if (IsLocalPlayer()) InvalidateWindow(WC_REPLACE_VEHICLE, GetEngine(old_engine_type)->type);
+
+			return cost;
 		}
 
 		case 4:
diff --git a/vehicle_gui.c b/vehicle_gui.c
--- a/vehicle_gui.c
+++ b/vehicle_gui.c
@@ -940,14 +940,12 @@ static void ReplaceVehicleWndProc(Window
 					EngineID veh_from = WP(w, replaceveh_d).sel_engine[0];
 					EngineID veh_to = WP(w, replaceveh_d).sel_engine[1];
 					DoCommandP(0, 3, veh_from + (veh_to << 16), NULL, CMD_REPLACE_VEHICLE);
-					SetWindowDirty(w);
 					break;
 				}
 
 				case 6: { /* Stop replacing */
 					EngineID veh_from = WP(w, replaceveh_d).sel_engine[0];
 					DoCommandP(0, 3, veh_from + (INVALID_ENGINE << 16), NULL, CMD_REPLACE_VEHICLE);
-					SetWindowDirty(w);
 					break;
 				}