diff --git a/lib/appenders/logstashUDP.js b/lib/appenders/logstashUDP.js
index f460fb6..51d2b74 100755
--- a/lib/appenders/logstashUDP.js
+++ b/lib/appenders/logstashUDP.js
@@ -62,9 +62,11 @@ function logstashUDP(config, layout) {
     /* eslint no-prototype-builtins:1,no-restricted-syntax:[1, "ForInStatement"] */
     if (loggingEvent.data.length > 1) {
       const secondEvData = loggingEvent.data[1];
-      Object.keys(secondEvData).forEach((key) => {
-        fields[key] = secondEvData[key];
-      });
+      if ((secondEvData !== undefined) && (secondEvData !== null)) {
+        Object.keys(secondEvData).forEach((key) => {
+          fields[key] = secondEvData[key];
+        });
+      }
     }
     fields.level = loggingEvent.level.levelStr;
     fields.category = loggingEvent.categoryName;
diff --git a/test/tap/logstashUDP-test.js b/test/tap/logstashUDP-test.js
index c2cb8a1..d04e2f5 100644
--- a/test/tap/logstashUDP-test.js
+++ b/test/tap/logstashUDP-test.js
@@ -186,6 +186,44 @@ test('logstashUDP appender', (batch) => {
     t.end();
   });
 
+  batch.test('Send null as argument', (t) => {
+    const setup = setupLogging('myLogger', {
+      host: '127.0.0.1',
+      port: 10001,
+      type: 'logstashUDP',
+      category: 'myLogger',
+      layout: {
+        type: 'dummy'
+      }
+    });
+
+    const msg = 'test message with null';
+    setup.logger.info(msg, null);
+    const json = JSON.parse(setup.results.buffer.toString());
+
+    t.equal(json.message, msg);
+    t.end();
+  });
+
+  batch.test('Send undefined as argument', (t) => {
+    const setup = setupLogging('myLogger', {
+      host: '127.0.0.1',
+      port: 10001,
+      type: 'logstashUDP',
+      category: 'myLogger',
+      layout: {
+        type: 'dummy'
+      }
+    });
+
+    const msg = 'test message with undefined';
+    setup.logger.info(msg, undefined);
+    const json = JSON.parse(setup.results.buffer.toString());
+
+    t.equal(json.message, msg);
+    t.end();
+  });
+
   batch.test('shutdown should close sockets', (t) => {
     const setup = setupLogging('myLogger', {
       host: '127.0.0.1',