--- old/src/java.base/share/classes/java/net/ProtocolException.java	2019-08-27 17:28:02.018324386 -0700
+++ new/src/java.base/share/classes/java/net/ProtocolException.java	2019-08-27 17:28:01.842324386 -0700
@@ -36,6 +36,7 @@
  */
 public
 class ProtocolException extends IOException {
+    @java.io.Serial
     private static final long serialVersionUID = -6098449442062388080L;
 
     /**