diff --git a/src/tilematrix_type.hpp b/src/tilematrix_type.hpp
index ad22a86..f4a43ae 100644
--- a/src/tilematrix_type.hpp
+++ b/src/tilematrix_type.hpp
@@ -98,16 +98,14 @@ class TileMatrix {
 		uint tile_y = (TileY(tile) / N) * N;
 		uint w = N, h = N;
 
-		if (tile_x >= extend * N) {
-			tile_x -= extend * N;
-			w += extend * N;
-		}
-		if (tile_y >= extend * N) {
-			tile_y -= extend * N;
-			h += extend * N;
-		}
-		if (tile_x + w < MapSizeX() - extend * N) w += extend * N;
-		if (tile_y + h < MapSizeY() - extend * N) h += extend * N;
+		w += min(extend * N, tile_x);
+		h += min(extend * N, tile_y);
+
+		tile_x -= min(extend * N, tile_x);
+		tile_y -= min(extend * N, tile_y);
+
+		w += min(extend * N, MapSizeX() - tile_x - w);
+		h += min(extend * N, MapSizeY() - tile_y - h);
 
 		return TileArea(TileXY(tile_x, tile_y), w, h);
 	}