diff --git a/js/pacosako.js b/js/pacosako.js
index dff585e..24121b8 100644
--- a/js/pacosako.js
+++ b/js/pacosako.js
@@ -712,7 +712,7 @@ class Game {
          const from = queue[0].from;
          queue = queue.slice(1);
 
-         seen.add(game.toString());
+         seen.add(game._board.toString());
 
          /* look for another piece that can reach the king or continue the chain */
          const pairs = [...game.board.findPieces(other, true, true)];