diff --git a/src/water_cmd.cpp b/src/water_cmd.cpp
index d6ce6c4821..e877618eb8 100644
--- a/src/water_cmd.cpp
+++ b/src/water_cmd.cpp
@@ -198,16 +198,22 @@ static CommandCost RemoveShipDepot(TileIndex tile, DoCommandFlag flags)
  */
 static CommandCost DoBuildLock(TileIndex tile, DiagDirection dir, DoCommandFlag flags)
 {
+	CommandCost cost(EXPENSES_CONSTRUCTION);
+
 	/* middle tile */
 	CommandCost ret = DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
 	if (ret.Failed()) return ret;
+	cost.AddCost(ret);
 
 	int delta = TileOffsByDiagDir(dir);
 	/* lower tile */
 	WaterClass wc_lower = IsWaterTile(tile - delta) ? GetWaterClass(tile - delta) : WATER_CLASS_CANAL;
 
-	ret = DoCommand(tile - delta, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
-	if (ret.Failed()) return ret;
+	if (!IsWaterTile(tile - delta)) {
+		ret = DoCommand(tile - delta, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
+		if (ret.Failed()) return ret;
+		cost.AddCost(ret);
+	}
 	if (GetTileSlope(tile - delta, NULL) != SLOPE_FLAT) {
 		return_cmd_error(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
 	}
@@ -215,8 +221,11 @@ static CommandCost DoBuildLock(TileIndex tile, DiagDirection dir, DoCommandFlag
 	/* upper tile */
 	WaterClass wc_upper = IsWaterTile(tile + delta) ? GetWaterClass(tile + delta) : WATER_CLASS_CANAL;
 
-	ret = DoCommand(tile + delta, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
-	if (ret.Failed()) return ret;
+	if (!IsWaterTile(tile + delta)) {
+		ret = DoCommand(tile + delta, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
+		if (ret.Failed()) return ret;
+		cost.AddCost(ret);
+	}
 	if (GetTileSlope(tile + delta, NULL) != SLOPE_FLAT) {
 		return_cmd_error(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
 	}
@@ -235,8 +244,9 @@ static CommandCost DoBuildLock(TileIndex tile, DiagDirection dir, DoCommandFlag
 		MarkCanalsAndRiversAroundDirty(tile - delta);
 		MarkCanalsAndRiversAroundDirty(tile + delta);
 	}
+	cost.AddCost(_price[PR_CLEAR_WATER] * 22 >> 3);
 
-	return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_CLEAR_WATER] * 22 >> 3);
+	return cost;
 }
 
 /** Remove a lock.