diff --git a/src/main/java/net/floodlightcontroller/linkdiscovery/internal/LinkDiscoveryManager.java b/src/main/java/net/floodlightcontroller/linkdiscovery/internal/LinkDiscoveryManager.java
index ff27401d0aa954c17d96b02bccd0e4b491c8870d..99dfc0a34a6d3f47029c9ae3023dca5d1236b0e1 100644
--- a/src/main/java/net/floodlightcontroller/linkdiscovery/internal/LinkDiscoveryManager.java
+++ b/src/main/java/net/floodlightcontroller/linkdiscovery/internal/LinkDiscoveryManager.java
@@ -1477,6 +1477,8 @@ public class LinkDiscoveryManager implements IOFMessageListener,
         }
 
         IOFSwitch iofSwitch = floodlightProvider.getSwitches().get(sw);
+        if (iofSwitch == null) return;
+
         if (autoPortFastFeature && iofSwitch.isFastPort(p)) {
             // Do nothing as the port is a fast port.
             return;
diff --git a/src/main/java/net/floodlightcontroller/topology/TopologyInstance.java b/src/main/java/net/floodlightcontroller/topology/TopologyInstance.java
index 06bb592584c40abc77d9d0d36831485640949150..7bc878614d124540d3165d42f7fa35088caf78e8 100644
--- a/src/main/java/net/floodlightcontroller/topology/TopologyInstance.java
+++ b/src/main/java/net/floodlightcontroller/topology/TopologyInstance.java
@@ -479,6 +479,12 @@ public class TopologyInstance {
             return true;
         }
 
+        @Override
+        public int hashCode() {
+            assert false : "hashCode not designed";
+            return 42;
+        }
+
         private TopologyInstance getOuterType() {
             return TopologyInstance.this;
         }