--- old/src/java.base/share/classes/java/time/ZoneRegion.java	2019-08-27 17:28:34.626324386 -0700
+++ new/src/java.base/share/classes/java/time/ZoneRegion.java	2019-08-27 17:28:34.446324386 -0700
@@ -92,6 +92,7 @@
     /**
      * Serialization version.
      */
+    @java.io.Serial
     private static final long serialVersionUID = 8386373296231747096L;
     /**
      * The time-zone ID, not null.
@@ -189,6 +190,7 @@
      *
      * @return the instance of {@code Ser}, not null
      */
+    @java.io.Serial
     private Object writeReplace() {
         return new Ser(Ser.ZONE_REGION_TYPE, this);
     }
@@ -199,6 +201,7 @@
      * @param s the stream to read
      * @throws InvalidObjectException always
      */
+    @java.io.Serial
     private void readObject(ObjectInputStream s) throws InvalidObjectException {
         throw new InvalidObjectException("Deserialization via serialization delegate");
     }