src/java.management/share/classes/sun/management/StackTraceElementCompositeData.java

@@ -146,11 +146,11 @@
 
         CompositeType ct = cd.getCompositeType();
         if (!isTypeMatched(stackTraceElementCompositeType, ct)) {
             if (!isTypeMatched(stackTraceElementV6CompositeType, ct)) {
                 throw new IllegalArgumentException(
-                    "Unexpected composite type for StackTraceElement");
+                    "Unexpected composite type for StackTraceElement: " + ct);
             }
         }
     }
 
     static boolean isV6Attribute(String name) {