diff --git a/core/api/src/main/java/org/onosproject/ui/model/topo/UiRegion.java b/core/api/src/main/java/org/onosproject/ui/model/topo/UiRegion.java
index de4c816f..4fe24b6 100644
--- a/core/api/src/main/java/org/onosproject/ui/model/topo/UiRegion.java
+++ b/core/api/src/main/java/org/onosproject/ui/model/topo/UiRegion.java
@@ -37,7 +37,7 @@
  */
 public class UiRegion extends UiNode {
 
-    private static final String NULL_NAME = "(root)";
+    public static final String NULL_NAME = "(root)";
     private static final String NO_NAME = "???";
     private static final String MEMO_ADDED = "added";
 
@@ -338,9 +338,11 @@
                 return isRegionRelevant(((UiRegion) event.subject()).id());
 
             case DEVICE_ADDED_OR_UPDATED:
+                final UiDevice uiDevice = (UiDevice) event.subject();
                 if (MEMO_ADDED.equalsIgnoreCase(event.memo()) &&
-                        regionId.toString().equalsIgnoreCase(
-                          ((UiDevice) event.subject()).regionId().toString())) {
+                        uiDevice.regionId() != null &&
+                        regionId.equals(
+                          ((UiDevice) event.subject()).regionId())) {
                     return true;
                 } else {
                     return isDeviceRelevant(((UiDevice) event.subject()).id());
@@ -360,7 +362,7 @@
                                 uiHost.regionId().toString())) {
                     return true;
                 } else {
-                    return isDeviceRelevant(((UiDevice) event.subject()).id());
+                    return isHostRelevant(((UiHost) event.subject()).id());
                 }
             case HOST_MOVED:
             case HOST_REMOVED:
@@ -375,6 +377,10 @@
         return deviceIds.contains(deviceId);
     }
 
+    private boolean isHostRelevant(HostId hostId) {
+        return hostIds.contains(hostId);
+    }
+
     private boolean isLinkRelevant(UiLink uiLink) {
         if (uiLink instanceof UiDeviceLink) {
             UiDeviceLink uiDeviceLink = (UiDeviceLink) uiLink;