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

@@ -127,10 +127,11 @@
   * This class is immutable and thread-safe.
   *
   * @since 1.8
   */
  @jdk.internal.ValueBased
+ @jdk.internal.MigratedValueClass
  public final class YearMonth
          implements Temporal, TemporalAdjuster, Comparable<YearMonth>, Serializable {
  
      /**
       * Serialization version.