diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/messaging/MessageSubject.java b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/messaging/MessageSubject.java
index ee3e789..43df15f 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/cluster/messaging/MessageSubject.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/cluster/messaging/MessageSubject.java
@@ -45,4 +45,9 @@
         MessageSubject that = (MessageSubject) obj;
         return Objects.equals(this.value, that.value);
     }
+
+    // for serializer
+    protected MessageSubject() {
+        this.value = "";
+    }
 }
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/InternalDeviceEvent.java b/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/InternalDeviceEvent.java
index 26f1d7f..4214384 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/InternalDeviceEvent.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/InternalDeviceEvent.java
@@ -35,4 +35,11 @@
     public Timestamped<DeviceDescription> deviceDescription() {
         return deviceDescription;
     }
+
+    // for serializer
+    protected InternalDeviceEvent() {
+        this.providerId = null;
+        this.deviceId = null;
+        this.deviceDescription = null;
+    }
 }
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/InternalPortEvent.java b/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/InternalPortEvent.java
index 48e3be6..64e77ca 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/InternalPortEvent.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/InternalPortEvent.java
@@ -37,4 +37,11 @@
     public Timestamped<List<PortDescription>> portDescriptions() {
         return portDescriptions;
     }
+
+    // for serializer
+    protected InternalPortEvent() {
+        this.providerId = null;
+        this.deviceId = null;
+        this.portDescriptions = null;
+    }
 }
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/InternalPortStatusEvent.java b/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/InternalPortStatusEvent.java
index 0bdfdbf..7d3854b 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/InternalPortStatusEvent.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/device/impl/InternalPortStatusEvent.java
@@ -35,4 +35,11 @@
     public Timestamped<PortDescription> portDescription() {
         return portDescription;
     }
+
+    // for serializer
+    protected InternalPortStatusEvent() {
+        this.providerId = null;
+        this.deviceId = null;
+        this.portDescription = null;
+    }
 }