diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/HummerMessage.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/HummerMessage.kt
index 6c402b688..201cf26a8 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/HummerMessage.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/HummerMessage.kt
@@ -282,7 +282,7 @@ sealed class FlashImage : MessageContent, HummerMessage() {
             }
         }
 
-    override fun toString(): String = stringValue!!
+    final override fun toString(): String = stringValue!!
     override fun contentToString(): String = "[闪照]"
 }