src/java.base/share/classes/java/net/UnknownHostException.java

@@ -33,10 +33,11 @@
  * @author  Jonathan Payne
  * @since   1.0
  */
 public
 class UnknownHostException extends IOException {
+    @java.io.Serial
     private static final long serialVersionUID = -4639126076052875403L;
 
     /**
      * Constructs a new {@code UnknownHostException} with the
      * specified detail message.