diff --git a/core/api/src/main/java/org/onosproject/net/DefaultAnnotations.java b/core/api/src/main/java/org/onosproject/net/DefaultAnnotations.java
index 13e74b8..3911d0e 100644
--- a/core/api/src/main/java/org/onosproject/net/DefaultAnnotations.java
+++ b/core/api/src/main/java/org/onosproject/net/DefaultAnnotations.java
@@ -189,6 +189,11 @@
         throw new IllegalArgumentException("Expecting HashMap instance");
     }
 
+    @Override
+    public String toString() {
+        return (map == null) ? "null" : map.toString();
+    }
+
     /**
      * Facility for gradually building model annotations.
      */