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

@@ -34,10 +34,11 @@
  * @author  Chris Warth
  * @since   1.0
  */
 public
 class ProtocolException extends IOException {
+    @java.io.Serial
     private static final long serialVersionUID = -6098449442062388080L;
 
     /**
      * Constructs a new {@code ProtocolException} with the
      * specified detail message.