diff --git a/server.py b/server.py
index 9738b04..61f97a3 100644
--- a/server.py
+++ b/server.py
@@ -299,16 +299,23 @@ def retrieve_tile(meta, offset, cache_info):
     )
 
 
+def is_valid_tile_request(z, x, y):
+    return (0 <= z < 20) and (0 <= x < 2**z) and (0 <= y < 2**z)
+
+
 @tile_bp.route('/tilezen/vector/v1/<int:tile_pixel_size>/all/<int:z>/<int:x>/<int:y>.<fmt>')
 @tile_bp.route('/tilezen/vector/v1/all/<int:z>/<int:x>/<int:y>.<fmt>')
 def handle_tile(z, x, y, fmt, tile_pixel_size=None):
-    requested_tile = TileRequest(z, x, y, fmt)
+    if not is_valid_tile_request(z, x, y):
+        return abort(400, "Requested tile out of range.")
 
     tile_pixel_size = tile_pixel_size or 256
     tile_size = tile_pixel_size / 256
     if tile_size != int(tile_size):
         return abort(400, "Invalid tile size. %s is not a multiple of 256." % tile_pixel_size)
 
+    requested_tile = TileRequest(z, x, y, fmt)
+
     tile_size = int(tile_size)
 
     meta, offset = meta_and_offset(
diff --git a/tests.py b/tests.py
index 280da87..794d434 100644
--- a/tests.py
+++ b/tests.py
@@ -127,6 +127,25 @@ def test_zoom_zero(self):
         self.assertTileEquals(TileRequest(1, 0, 1, 'zip'), meta)
         self.assertTileEquals(TileRequest(2, 2, 3, 'json'), offset)
 
+    def test_valid_tile_request(self):
+        from server import is_valid_tile_request
+
+        # The world
+        self.assertTrue(is_valid_tile_request(0, 0, 0))
+        # Home sweet home
+        self.assertTrue(is_valid_tile_request(15, 15800, 23583))
+        # Negative!
+        self.assertFalse(is_valid_tile_request(-1, 15800, 23583))
+        self.assertFalse(is_valid_tile_request(15, -23, 23583))
+        self.assertFalse(is_valid_tile_request(15, 15800, -12))
+        # Too big!
+        self.assertFalse(is_valid_tile_request(15, 2401239, 23583))
+        self.assertFalse(is_valid_tile_request(15, 15800, 2341583))
+        self.assertFalse(is_valid_tile_request(12, 4096, 1844674407))
+        # In the corners
+        self.assertFalse(is_valid_tile_request(16, 65535, 10110))
+        self.assertFalse(is_valid_tile_request(16, 65536, 10111))
+
     def test_compute_key(self):
         from server import compute_key, KeyFormatType