Index: src/test/java/org/apache/logging/log4j/message/StructuredDataMessageTest.java
===================================================================
--- src/test/java/org/apache/logging/log4j/message/StructuredDataMessageTest.java	(revision 1398855)
+++ src/test/java/org/apache/logging/log4j/message/StructuredDataMessageTest.java	(working copy)
@@ -31,8 +31,16 @@
         StructuredDataMessage msg = new StructuredDataMessage("MsgId@12345", testMsg, "Alert");
         msg.put("message", testMsg);
         msg.put("project", "Log4j");
+        msg.put("memo", "This is a very long test memo to prevent regression of LOG4J2-114");
         String result = msg.getFormattedMessage();
         String expected = "Alert [MsgId@12345 message=\"Test message {}\" project=\"Log4j\"] Test message {}";
         assertEquals(expected, result);
     }
+
+    @Test(expected=IllegalArgumentException.class)
+    public void testMsgWithKeyTooLong() {
+        String testMsg = "Test message {}";
+        StructuredDataMessage msg = new StructuredDataMessage("MsgId@12345", testMsg, "Alert");
+        msg.put("This is a very long key that will violate the key length validation", "Testing");
+    }
 }