diff --git a/mirai-core-api/src/commonMain/kotlin/contact/announcement/OfflineAnnouncement.kt b/mirai-core-api/src/commonMain/kotlin/contact/announcement/OfflineAnnouncement.kt
index b30769c66..17b758b9e 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/announcement/OfflineAnnouncement.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/announcement/OfflineAnnouncement.kt
@@ -31,6 +31,9 @@ public sealed interface OfflineAnnouncement : Announcement {
     public companion object {
         public const val SERIAL_NAME: String = "OfflineAnnouncement"
 
+        @JvmStatic
+        public fun serializer(): KSerializer<OfflineAnnouncement> = Serializer
+
         /**
          * 创建 [OfflineAnnouncement]. 若 [announcement] 类型为 [OfflineAnnouncement] 则直接返回 [announcement].
          */