diff --git a/dev/js/src/match/treearc.js b/dev/js/src/match/treearc.js
index e7d7ac3..afcd187 100644
--- a/dev/js/src/match/treearc.js
+++ b/dev/js/src/match/treearc.js
@@ -610,7 +610,7 @@
 
       // Add sorted arcs and anchors
       this._sortedArcs    = lengthSort(sortedArcs, false);
-      this._sortedAnchors = lengthSort(Object.keys(anchors), true);
+      this._sortedAnchors = lengthSort(Object.values(anchors), true);
     },
 
     /**