diff --git a/matrix_appservice_kakaotalk/matrix.py b/matrix_appservice_kakaotalk/matrix.py
index 1930502..dc8a80b 100644
--- a/matrix_appservice_kakaotalk/matrix.py
+++ b/matrix_appservice_kakaotalk/matrix.py
@@ -157,7 +157,8 @@ class MatrixHandler(BaseMatrixHandler):
         if not user.is_connected:
             return
         message = await DBMessage.get_by_mxid(event_id, portal.mxid)
-        await user.client.mark_read(portal.channel_props, message.ktid)
+        if message:
+            await user.client.mark_read(portal.channel_props, message.ktid)
 
     async def handle_ephemeral_event(
         self, evt: ReceiptEvent | Event