diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/CustomMessage.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/CustomMessage.kt
index c18718c09..7d11bc193 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/CustomMessage.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/CustomMessage.kt
@@ -190,8 +190,6 @@ abstract class CustomMessageMetadata : CustomMessage(), MessageMetadata {
 
     final override fun toString(): String =
         "[mirai:custom:${getFactory().typeName}:${String(customToString())}]"
-
-    final override fun contentToString(): String = ""
 }
 
 
diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/Message.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/Message.kt
index 04adf1fe6..88ec92411 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/Message.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/Message.kt
@@ -297,7 +297,13 @@ interface SingleMessage : Message {
  *
  * @see ConstrainSingle 约束一个 [MessageChain] 中只存在这一种类型的元素
  */
-interface MessageMetadata : SingleMessage
+interface MessageMetadata : SingleMessage {
+    /**
+     * 返回空字符串
+     */
+    @Suppress("WRONG_MODIFIER_CONTAINING_DECLARATION")
+    final override fun contentToString(): String = ""
+}
 
 /**
  * 约束一个 [MessageChain] 中只存在这一种类型的元素. 新元素将会替换旧元素, 保持原顺序.
diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/MessageSource.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/MessageSource.kt
index 9b96bb857..7e58f2c60 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/MessageSource.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/MessageSource.kt
@@ -132,11 +132,6 @@ sealed class MessageSource : Message, MessageMetadata, ConstrainSingle<MessageSo
      * 返回 `"[mirai:source:$id,$internalId]"`
      */
     final override fun toString(): String = "[mirai:source:$id,$internalId]"
-
-    /**
-     * 返回空字符串, 因 [MessageMetadata] 的约束.
-     */
-    final override fun contentToString(): String = ""
 }
 
 
diff --git a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/QuoteReply.kt b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/QuoteReply.kt
index 7bda88ce6..fd424fd42 100644
--- a/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/QuoteReply.kt
+++ b/mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/QuoteReply.kt
@@ -55,7 +55,6 @@ class QuoteReply(val source: MessageSource) : Message, MessageMetadata, Constrai
     override val key: Message.Key<QuoteReply> get() = Key
 
     override fun toString(): String = "[mirai:quote:${source.id},${source.internalId}]"
-    override fun contentToString(): String = ""
     override fun equals(other: Any?): Boolean = other is QuoteReply && other.source == this.source
     override fun hashCode(): Int = source.hashCode()
 }
diff --git a/mirai-core/src/commonTest/kotlin/net/mamoe/mirai/message.data/ConstrainSingleTest.kt b/mirai-core/src/commonTest/kotlin/net/mamoe/mirai/message.data/ConstrainSingleTest.kt
index 2e2d8498d..295082f77 100644
--- a/mirai-core/src/commonTest/kotlin/net/mamoe/mirai/message.data/ConstrainSingleTest.kt
+++ b/mirai-core/src/commonTest/kotlin/net/mamoe/mirai/message.data/ConstrainSingleTest.kt
@@ -26,10 +26,6 @@ internal class TestConstrainSingleMessage : ConstrainSingle<TestConstrainSingleM
 
     override fun toString(): String = "<TestConstrainSingleMessage#${super.hashCode()}>"
 
-    override fun contentToString(): String {
-        return ""
-    }
-
     override val key: Message.Key<TestConstrainSingleMessage>
         get() = Key
 }