diff --git a/core/store/persistence/src/main/java/org/onosproject/persistence/impl/PersistentSet.java b/core/store/persistence/src/main/java/org/onosproject/persistence/impl/PersistentSet.java
index 19279d8..067329c 100644
--- a/core/store/persistence/src/main/java/org/onosproject/persistence/impl/PersistentSet.java
+++ b/core/store/persistence/src/main/java/org/onosproject/persistence/impl/PersistentSet.java
@@ -112,7 +112,7 @@
 
     @Override
     public boolean add(E item) {
-        checkNotNull("Item to be added cannot be null.");
+        checkNotNull(item, "Item to be added cannot be null.");
         return items.add(serializer.encode(item));
     }