diff --git a/src/logic/future_moves.rs b/src/logic/future_moves.rs
index 1a43cdf..8a9492a 100644
--- a/src/logic/future_moves.rs
+++ b/src/logic/future_moves.rs
@@ -542,12 +542,10 @@ impl FutureMoves {
             .filter(|&((_, keep), _)| keep) // filter out un-related nodes
             .map(|((old_idx, _), node)| (old_idx, node))
             .enumerate() // new_idx
-            .map(|(new_idx, (old_idx, node))| ((new_idx, old_idx), node))
+            .map(|(new_idx, (old_idx, node))| ((old_idx, new_idx), node))
             .unzip();
 
-        for (new_idx, old_idx) in indexes {
-            index_map.insert(old_idx, new_idx);
-        }
+        index_map.extend(indexes);
 
         self.arena = moves
             .into_iter()