diff -r 18863bf3501f -r e0b8b019d2f5 src/java.base/share/classes/java/time/Instant.java
--- a/src/java.base/share/classes/java/time/Instant.java	Thu Aug 29 18:52:30 2019 -0400
+++ b/src/java.base/share/classes/java/time/Instant.java	Thu Aug 29 16:31:34 2019 -0700
@@ -245,6 +245,7 @@
     /**
      * Serialization version.
      */
+    @java.io.Serial
     private static final long serialVersionUID = -665713676816604388L;
 
     /**
@@ -1342,6 +1343,7 @@
      *
      * @return the instance of {@code Ser}, not null
      */
+    @java.io.Serial
     private Object writeReplace() {
         return new Ser(Ser.INSTANT_TYPE, this);
     }
@@ -1352,6 +1354,7 @@
      * @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");
     }