diff --git a/core/net/src/test/java/org/onosproject/net/flow/impl/FlowRuleManagerTest.java b/core/net/src/test/java/org/onosproject/net/flow/impl/FlowRuleManagerTest.java
index 1e621f5..235699d 100644
--- a/core/net/src/test/java/org/onosproject/net/flow/impl/FlowRuleManagerTest.java
+++ b/core/net/src/test/java/org/onosproject/net/flow/impl/FlowRuleManagerTest.java
@@ -569,7 +569,7 @@
 
         @Override
         public Set<Criterion> criteria() {
-            return null;
+            return Collections.emptySet();
         }
 
         @Override