--- old/src/java.base/share/classes/java/net/PortUnreachableException.java	2019-08-27 17:28:01.522324386 -0700
+++ new/src/java.base/share/classes/java/net/PortUnreachableException.java	2019-08-27 17:28:01.306324386 -0700
@@ -33,6 +33,7 @@
  */
 
 public class PortUnreachableException extends SocketException {
+    @java.io.Serial
     private static final long serialVersionUID = 8462541992376507323L;
 
     /**