diff --git a/lib/hcluster.js b/lib/hcluster.js
index 7e4fdac..d4ffc19 100644
--- a/lib/hcluster.js
+++ b/lib/hcluster.js
@@ -80,7 +80,8 @@ HierarchicalClustering.prototype = {
          left: c1,
          right: c2,
          key: c1.key,
-         size: c1.size + c2.size
+         size: c1.size + c2.size,
+         distance: min
       };
 
       this.clusters[c1.index] = merged;