diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/differentialentropy/UnweightedDoubleReservoirSample.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/differentialentropy/UnweightedDoubleReservoirSample.java
index d9c7ea87dbc9..f8bd4c083798 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/differentialentropy/UnweightedDoubleReservoirSample.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/differentialentropy/UnweightedDoubleReservoirSample.java
@@ -121,7 +121,7 @@ public int getTotalPopulationCount()
     }
 
     @Override
-    public UnweightedDoubleReservoirSample clone()
+    public final UnweightedDoubleReservoirSample clone()
     {
         return new UnweightedDoubleReservoirSample(this);
     }
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/differentialentropy/WeightedDoubleReservoirSample.java b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/differentialentropy/WeightedDoubleReservoirSample.java
index 8be48379d0f7..aeda45449408 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/aggregation/differentialentropy/WeightedDoubleReservoirSample.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/aggregation/differentialentropy/WeightedDoubleReservoirSample.java
@@ -107,7 +107,7 @@ public void mergeWith(WeightedDoubleReservoirSample other)
     }
 
     @Override
-    public WeightedDoubleReservoirSample clone()
+    public final WeightedDoubleReservoirSample clone()
     {
         return new WeightedDoubleReservoirSample(this);
     }