diff --git a/src/main/java/dev/osm/mapsplit/AbstractOsmMap.java b/src/main/java/dev/osm/mapsplit/AbstractOsmMap.java
index 399985c..6308eaa 100644
--- a/src/main/java/dev/osm/mapsplit/AbstractOsmMap.java
+++ b/src/main/java/dev/osm/mapsplit/AbstractOsmMap.java
@@ -89,41 +89,49 @@ public List<Integer> getAllTiles(long key) {
 
         int tx = tileX(value);
         int ty = tileY(value);
-        int neighbour = neighbour(value);
 
         List<Integer> result;
 
         if ((value & TILE_EXT_MASK) != 0) {
             int idx = (int) (value & TILE_EXT_INDEX_MASK);
-            result = new ArrayList<>(asList(extendedSet[idx]));
+            result = asList(extendedSet[idx]);
+            result.add(TileCoord.encode(tx, ty));
         } else {
             result = parseMarker(value);
+            result.add(TileCoord.encode(tx, ty));
+            // add possible neighbours
+            int neighbour = neighbour(value);
+            if ((neighbour & OsmMap.NEIGHBOURS_EAST) != 0) {
+                addTileIfNotPresent(tx, ty, result);
+            }
+            if ((neighbour & OsmMap.NEIGHBOURS_SOUTH) != 0) {
+                addTileIfNotPresent(tx, ty + 1, result);
+            }
+            if ((neighbour & OsmMap.NEIGHBOURS_SOUTH_EAST) == OsmMap.NEIGHBOURS_SOUTH_EAST) {
+                addTileIfNotPresent(tx + 1, ty + 1, result);
+            }
         }
+        return result;
+    }
 
-        // TODO: some tiles (neighbour-tiles) might be double-included in the list, is this a problem?!
-
-        // add the tile (and possible neighbours)
-        result.add(TileCoord.encode(tx, ty));
-        if ((neighbour & OsmMap.NEIGHBOURS_EAST) != 0) {
-            result.add(TileCoord.encode(tx + 1, ty));
-        }
-        if ((neighbour & OsmMap.NEIGHBOURS_SOUTH) != 0) {
-            result.add(TileCoord.encode(tx, ty + 1));
-        }
-        if ((neighbour & OsmMap.NEIGHBOURS_SOUTH_EAST) == OsmMap.NEIGHBOURS_SOUTH_EAST) {
-            result.add(TileCoord.encode(tx + 1, ty + 1));
+    /**
+     * Add an encoded tile to result if not already present
+     * 
+     * @param tx tile x coord
+     * @param ty tile y coord
+     * @param result a List holding the tiles
+     */
+    public void addTileIfNotPresent(int tx, int ty, @NotNull List<Integer> result) {
+        int t = TileCoord.encode(tx + 1, ty);
+        if (!result.contains(t)) {
+            result.add(t);
         }
-
-        return result;
     }
 
     @Override
     public void updateInt(long key, Collection<Integer> tiles) {
-
         List<Long> longTiles = tiles.stream().map(tile -> createValue(TileCoord.decodeX(tile), TileCoord.decodeY(tile), NEIGHBOURS_NONE)).collect(toList());
-
         this.update(key, longTiles);
-
     }
 
     /**
@@ -361,12 +369,9 @@ private static int[] merge(@NotNull int[] old, @NotNull int[] add, int len) {
     @NotNull
     private static List<Integer> asList(@NotNull int[] set) {
         List<Integer> result = new ArrayList<>();
-
         for (int i = 0; i < set.length; i++) {
             result.add(set[i]);
         }
-
         return result;
     }
-
 }