diff --git a/core/api/src/main/java/org/onosproject/net/flow/criteria/EthCriterion.java b/core/api/src/main/java/org/onosproject/net/flow/criteria/EthCriterion.java
index f7c6f48..8bdfd2c 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/criteria/EthCriterion.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/criteria/EthCriterion.java
@@ -77,7 +77,9 @@
 
     @Override
     public String toString() {
-        return type().toString() + SEPARATOR + mac + "/" + mask;
+        return (mask != null) ?
+            type().toString() + SEPARATOR + mac + "/" + mask :
+            type().toString() + SEPARATOR + mac;
     }
 
     @Override