src/java.base/share/classes/java/time/Period.java

@@ -129,10 +129,11 @@
   * This class is immutable and thread-safe.
   *
   * @since 1.8
   */
  @jdk.internal.ValueBased
+ @jdk.internal.MigratedValueClass
  public final class Period
          implements ChronoPeriod, Serializable {
  
      /**
       * A constant for a period of zero.