diff --git a/mirai-core-api/src/commonMain/kotlin/contact/OtherClient.kt b/mirai-core-api/src/commonMain/kotlin/contact/OtherClient.kt
index f4b0a10ed..3e77881f1 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/OtherClient.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/OtherClient.kt
@@ -12,8 +12,12 @@
 package net.mamoe.mirai.contact
 
 import net.mamoe.mirai.Bot
+import net.mamoe.mirai.message.MessageReceipt
+import net.mamoe.mirai.message.data.Image
+import net.mamoe.mirai.message.data.Message
 import net.mamoe.mirai.utils.BotConfiguration.MiraiProtocol.ANDROID_PAD
 import net.mamoe.mirai.utils.BotConfiguration.MiraiProtocol.ANDROID_PHONE
+import net.mamoe.mirai.utils.ExternalImage
 
 /**
  * 其他设备. 如当 [Bot] 以 [ANDROID_PHONE] 登录时, 还可以有其他设备以 [ANDROID_PAD], iOS, PC 或其他设备登录.
@@ -33,6 +37,14 @@ public interface OtherClient : Contact {
      * 与 [Bot.id] 相同
      */
     public override val id: Long get() = bot.id
+
+    override suspend fun sendMessage(message: Message): MessageReceipt<OtherClient> {
+        throw UnsupportedOperationException("OtherClientImpl.sendMessage is not yet supported.")
+    }
+
+    override suspend fun uploadImage(image: ExternalImage): Image {
+        throw UnsupportedOperationException("OtherClientImpl.uploadImage is not yet supported.")
+    }
 }
 
 /**
diff --git a/mirai-core/src/commonMain/kotlin/contact/OtherClientImpl.kt b/mirai-core/src/commonMain/kotlin/contact/OtherClientImpl.kt
index 3a9efcb51..c853c2ae1 100644
--- a/mirai-core/src/commonMain/kotlin/contact/OtherClientImpl.kt
+++ b/mirai-core/src/commonMain/kotlin/contact/OtherClientImpl.kt
@@ -11,7 +11,6 @@ package net.mamoe.mirai.internal.contact
 
 import net.mamoe.mirai.Bot
 import net.mamoe.mirai.contact.ClientKind
-import net.mamoe.mirai.contact.Contact
 import net.mamoe.mirai.contact.OtherClient
 import net.mamoe.mirai.message.MessageReceipt
 import net.mamoe.mirai.message.data.Image
@@ -29,12 +28,12 @@ internal class OtherClientImpl(
     override val kind: ClientKind,
     val instanceInfo: InstanceInfo
 ) : OtherClient, AbstractContact(bot, coroutineContext) {
-    override suspend fun sendMessage(message: Message): MessageReceipt<Contact> {
-        TODO("Not yet implemented")
+    override suspend fun sendMessage(message: Message): MessageReceipt<OtherClient> {
+        throw UnsupportedOperationException("OtherClientImpl.sendMessage is not yet supported.")
     }
 
     override suspend fun uploadImage(image: ExternalImage): Image {
-        TODO("Not yet implemented")
+        throw UnsupportedOperationException("OtherClientImpl.uploadImage is not yet supported.")
     }
 
     override fun toString(): String {