diff --git a/src/main/java/org/opencord/aaa/AaaShowUsersCommand.java b/src/main/java/org/opencord/aaa/AaaShowUsersCommand.java
index e64a6fe..f05dd8a 100644
--- a/src/main/java/org/opencord/aaa/AaaShowUsersCommand.java
+++ b/src/main/java/org/opencord/aaa/AaaShowUsersCommand.java
@@ -46,13 +46,20 @@
         for (StateMachine stateMachine : StateMachine.sessionIdMap().values()) {
             String deviceId = stateMachine.supplicantConnectpoint().deviceId().toString();
             String portNum = stateMachine.supplicantConnectpoint().port().toString();
-            String username = new String(stateMachine.username());
-            String mac = stateMachine.supplicantAddress().toString();
+
+            String username = "UNKNOWN";
+            if (stateMachine.username() != null) {
+                username = new String(stateMachine.username());
+            }
+            String mac = "UNKNOWN";
+            if (stateMachine.supplicantAddress() != null) {
+                mac = stateMachine.supplicantAddress().toString();
+            }
 
             String nasPortId = devService.getPort(stateMachine.supplicantConnectpoint()).
                     annotations().value(AnnotationKeys.PORT_NAME);
 
-            String subsId = "Unknown";
+            String subsId = "UNKNOWN";
             SubscriberAndDeviceInformation subscriber = subsService.get(nasPortId);
             if (subscriber != null) {
                 subsId = subscriber.nasPortId();