--- old/src/java.base/share/classes/java/util/RegularEnumSet.java	2019-08-27 17:29:11.310324386 -0700
+++ new/src/java.base/share/classes/java/util/RegularEnumSet.java	2019-08-27 17:29:11.126324386 -0700
@@ -34,6 +34,7 @@
  * @serial exclude
  */
 class RegularEnumSet<E extends Enum<E>> extends EnumSet<E> {
+    @java.io.Serial
     private static final long serialVersionUID = 3411599620347842686L;
     /**
      * Bit vector representation of this set.  The 2^k bit indicates the