diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
index 579edf109c..a2dd019251 100644
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -1236,7 +1236,7 @@ static bool GrowTownWithRoad(const Town *t, TileIndex tile, RoadBits rcmd)
  */
 static bool CanRoadContinueIntoNextTile(const Town *t, const TileIndex tile, const DiagDirection road_dir)
 {
-	const int delta = TileOffsByDiagDir(road_dir); // +1 tile in the direction of the road
+	const TileIndexDiff delta = TileOffsByDiagDir(road_dir); // +1 tile in the direction of the road
 	TileIndex next_tile = tile + delta; // The tile beyond which must be connectable to the target tile
 	RoadBits rcmd = DiagDirToRoadBits(ReverseDiagDir(road_dir));
 	RoadType rt = GetTownRoadType();
@@ -1317,7 +1317,7 @@ static bool GrowTownWithBridge(const Town *t, const TileIndex tile, const DiagDi
 	uint bridge_length = 0;       // This value stores the length of the possible bridge
 	TileIndex bridge_tile = tile; // Used to store the other waterside
 
-	const int delta = TileOffsByDiagDir(bridge_dir);
+	const TileIndexDiff delta = TileOffsByDiagDir(bridge_dir);
 
 	/* To prevent really small towns from building disproportionately
 	 * long bridges, make the max a function of its population. */
@@ -1392,7 +1392,7 @@ static bool GrowTownWithTunnel(const Town *t, const TileIndex tile, const DiagDi
 	/* Assure that the tunnel is connectable to the start side */
 	if (!(GetTownRoadBits(TileAddByDiagDir(tile, ReverseDiagDir(tunnel_dir))) & DiagDirToRoadBits(tunnel_dir))) return false;
 
-	const int delta = TileOffsByDiagDir(tunnel_dir);
+	const TileIndexDiff delta = TileOffsByDiagDir(tunnel_dir);
 	int max_tunnel_length = 0;
 
 	/* There are two conditions for building tunnels: Under a mountain and under an obstruction. */
diff --git a/src/water_cmd.cpp b/src/water_cmd.cpp
index c86976397a..9d7dc389a8 100644
--- a/src/water_cmd.cpp
+++ b/src/water_cmd.cpp
@@ -302,7 +302,7 @@ static CommandCost DoBuildLock(TileIndex tile, DiagDirection dir, DoCommandFlag
 {
 	CommandCost cost(EXPENSES_CONSTRUCTION);
 
-	int delta = TileOffsByDiagDir(dir);
+	TileIndexDiff delta = TileOffsByDiagDir(dir);
 	CommandCost ret = EnsureNoVehicleOnGround(tile);
 	if (ret.Succeeded()) ret = EnsureNoVehicleOnGround(tile + delta);
 	if (ret.Succeeded()) ret = EnsureNoVehicleOnGround(tile - delta);