--- old/src/java.base/share/classes/sun/net/ftp/FtpProtocolException.java	2019-08-27 17:29:29.990324386 -0700
+++ new/src/java.base/share/classes/sun/net/ftp/FtpProtocolException.java	2019-08-27 17:29:29.798324386 -0700
@@ -32,6 +32,7 @@
  * @author      Jonathan Payne
  */
 public class FtpProtocolException extends Exception {
+    @java.io.Serial
     private static final long serialVersionUID = 5978077070276545054L;
     private final FtpReplyCode code;