diff --git a/src/main/java/org/apache/datasketches/hll/Union.java b/src/main/java/org/apache/datasketches/hll/Union.java
index 986537941..530f646f6 100644
--- a/src/main/java/org/apache/datasketches/hll/Union.java
+++ b/src/main/java/org/apache/datasketches/hll/Union.java
@@ -306,7 +306,7 @@ public byte[] toUpdatableByteArray() {
   @Override
   public String toString(final boolean summary, final boolean hllDetail,
       final boolean auxDetail, final boolean all) {
-    HllSketch clone = gadget.copy();
+    final HllSketch clone = gadget.copy();
     checkRebuildCurMinNumKxQ(clone);
     return clone.toString(summary, hllDetail, auxDetail, all);
   }