diff --git a/src/aircraft_cmd.cpp b/src/aircraft_cmd.cpp
index 6a7c9258e1..511dbe02a5 100644
--- a/src/aircraft_cmd.cpp
+++ b/src/aircraft_cmd.cpp
@@ -155,7 +155,7 @@ SpriteID Aircraft::GetImage(Direction direction) const
 		SpriteID sprite = GetCustomVehicleSprite(this, direction);
 		if (sprite != 0) return sprite;
 
-		spritenum = Engine::Get(this->engine_type)->image_index;
+		spritenum = Engine::Get(this->engine_type)->original_image_index;
 	}
 
 	return direction + _aircraft_sprite[spritenum];
@@ -183,7 +183,7 @@ static SpriteID GetAircraftIcon(EngineID engine)
 		SpriteID sprite = GetCustomVehicleIcon(engine, DIR_W);
 		if (sprite != 0) return sprite;
 
-		spritenum = Engine::Get(engine)->image_index;
+		spritenum = Engine::Get(engine)->original_image_index;
 	}
 
 	return DIR_W + _aircraft_sprite[spritenum];
diff --git a/src/engine.cpp b/src/engine.cpp
index 5e873f5a1b..bc0fb8a52f 100644
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -84,7 +84,7 @@ Engine::Engine(VehicleType type, EngineID base)
 
 		case VEH_TRAIN:
 			this->u.rail = _orig_rail_vehicle_info[base];
-			this->image_index = this->u.rail.image_index;
+			this->original_image_index = this->u.rail.image_index;
 			this->info.string_id = STR_VEHICLE_NAME_TRAIN_ENGINE_RAIL_KIRBY_PAUL_TANK_STEAM + base;
 
 			/* Set the default model life of original wagons to "infinite" */
@@ -94,19 +94,19 @@ Engine::Engine(VehicleType type, EngineID base)
 
 		case VEH_ROAD:
 			this->u.road = _orig_road_vehicle_info[base];
-			this->image_index = this->u.road.image_index;
+			this->original_image_index = this->u.road.image_index;
 			this->info.string_id = STR_VEHICLE_NAME_ROAD_MPS_REGAL_BUS + base;
 			break;
 
 		case VEH_SHIP:
 			this->u.ship = _orig_ship_vehicle_info[base];
-			this->image_index = this->u.ship.image_index;
+			this->original_image_index = this->u.ship.image_index;
 			this->info.string_id = STR_VEHICLE_NAME_SHIP_MPS_OIL_TANKER + base;
 			break;
 
 		case VEH_AIRCRAFT:
 			this->u.air = _orig_aircraft_vehicle_info[base];
-			this->image_index = this->u.air.image_index;
+			this->original_image_index = this->u.air.image_index;
 			this->info.string_id = STR_VEHICLE_NAME_AIRCRAFT_SAMPSON_U52 + base;
 			break;
 	}
diff --git a/src/engine_base.h b/src/engine_base.h
index 2f071f343f..bbf25b9fa6 100644
--- a/src/engine_base.h
+++ b/src/engine_base.h
@@ -26,7 +26,7 @@ struct Engine : EnginePool::PoolItem<&_engine_pool> {
 	uint8 preview_company_rank;
 	byte preview_wait;
 	CompanyMask company_avail;
-	uint8 image_index; ///< Original vehicle image index
+	uint8 original_image_index; ///< Original vehicle image index, thus the image index of the overridden vehicle
 	VehicleType type; ///< type, ie VEH_ROAD, VEH_TRAIN, etc.
 
 	EngineInfo info;
diff --git a/src/roadveh_cmd.cpp b/src/roadveh_cmd.cpp
index 832237c069..f2704e1d05 100644
--- a/src/roadveh_cmd.cpp
+++ b/src/roadveh_cmd.cpp
@@ -90,7 +90,7 @@ static SpriteID GetRoadVehIcon(EngineID engine)
 		SpriteID sprite = GetCustomVehicleIcon(engine, DIR_W);
 		if (sprite != 0) return sprite;
 
-		spritenum = Engine::Get(engine)->image_index;
+		spritenum = Engine::Get(engine)->original_image_index;
 	}
 
 	return DIR_W + _roadveh_images[spritenum];
@@ -105,7 +105,7 @@ SpriteID RoadVehicle::GetImage(Direction direction) const
 		sprite = GetCustomVehicleSprite(this, (Direction)(direction + 4 * IS_CUSTOM_SECONDHEAD_SPRITE(spritenum)));
 		if (sprite != 0) return sprite;
 
-		spritenum = Engine::Get(this->engine_type)->image_index;
+		spritenum = Engine::Get(this->engine_type)->original_image_index;
 	}
 
 	sprite = direction + _roadveh_images[spritenum];
diff --git a/src/ship_cmd.cpp b/src/ship_cmd.cpp
index 226460ce1b..15c150be2a 100644
--- a/src/ship_cmd.cpp
+++ b/src/ship_cmd.cpp
@@ -56,7 +56,7 @@ static SpriteID GetShipIcon(EngineID engine)
 		SpriteID sprite = GetCustomVehicleIcon(engine, DIR_W);
 		if (sprite != 0) return sprite;
 
-		spritenum = Engine::Get(engine)->image_index;
+		spritenum = Engine::Get(engine)->original_image_index;
 	}
 
 	return DIR_W + _ship_sprites[spritenum];
@@ -88,7 +88,7 @@ SpriteID Ship::GetImage(Direction direction) const
 		SpriteID sprite = GetCustomVehicleSprite(this, direction);
 		if (sprite != 0) return sprite;
 
-		spritenum = Engine::Get(this->engine_type)->image_index;
+		spritenum = Engine::Get(this->engine_type)->original_image_index;
 	}
 
 	return _ship_sprites[spritenum] + direction;
diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
index a8b620ec1a..253981a468 100644
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -603,7 +603,7 @@ SpriteID Train::GetImage(Direction direction) const
 		sprite = GetCustomVehicleSprite(this, (Direction)(direction + 4 * IS_CUSTOM_SECONDHEAD_SPRITE(spritenum)));
 		if (sprite != 0) return sprite;
 
-		spritenum = Engine::Get(this->engine_type)->image_index;
+		spritenum = Engine::Get(this->engine_type)->original_image_index;
 	}
 
 	sprite = GetDefaultTrainSprite(spritenum, direction);
@@ -625,7 +625,7 @@ static SpriteID GetRailIcon(EngineID engine, bool rear_head, int &y)
 			return sprite;
 		}
 
-		spritenum = Engine::Get(engine)->image_index;
+		spritenum = Engine::Get(engine)->original_image_index;
 	}
 
 	if (rear_head) spritenum++;