diff --git a/apps/dhcprelay/app/src/main/java/org/onosproject/dhcprelay/DhcpRelayManager.java b/apps/dhcprelay/app/src/main/java/org/onosproject/dhcprelay/DhcpRelayManager.java
index ad67681..b88c8c9 100644
--- a/apps/dhcprelay/app/src/main/java/org/onosproject/dhcprelay/DhcpRelayManager.java
+++ b/apps/dhcprelay/app/src/main/java/org/onosproject/dhcprelay/DhcpRelayManager.java
@@ -51,6 +51,7 @@
 import org.onosproject.dhcprelay.store.DhcpRelayStore;
 import org.onosproject.net.ConnectPoint;
 import org.onosproject.net.Device;
+import org.onosproject.net.DeviceId;
 import org.onosproject.net.Host;
 import org.onosproject.net.HostId;
 import org.onosproject.net.HostLocation;
@@ -142,7 +143,7 @@
             .build();
     private final Logger log = LoggerFactory.getLogger(getClass());
     private final InternalConfigListener cfgListener = new InternalConfigListener();
-    protected CopyOnWriteArraySet hostAutoRelearnEnabledDevices = new CopyOnWriteArraySet();
+    private CopyOnWriteArraySet<DeviceId> hostAutoRelearnEnabledDevices = new CopyOnWriteArraySet<DeviceId>();
 
     private final Set<ConfigFactory> factories = ImmutableSet.of(
             new ConfigFactory<ApplicationId, DefaultDhcpRelayConfig>(APP_SUBJECT_FACTORY,
@@ -787,6 +788,7 @@
                     .findFirst().orElse(null);
             if (senderInterface == null) {
                 log.warn("Cannot get sender interface for from packet, abort... vlan {}", vlanId.toString());
+                return;
             }
             MacAddress senderMacAddress = senderInterface.mac();
             byte[] senderIpAddress = IPv6.getLinkLocalAddress(senderMacAddress.toBytes());