diff --git a/pkg/common/storage/database/mgo/msg.go b/pkg/common/storage/database/mgo/msg.go
index f0665b03d..c70718f73 100644
--- a/pkg/common/storage/database/mgo/msg.go
+++ b/pkg/common/storage/database/mgo/msg.go
@@ -951,7 +951,7 @@ func (m *MsgMgo) GetLastMessageSeqByTime(ctx context.Context, conversationID str
 		{
 			"$match": bson.M{
 				"doc_id": bson.M{
-					"$regex": fmt.Sprintf("^%s", conversationID),
+					"$regex": fmt.Sprintf("^%s:", conversationID),
 				},
 			},
 		},
@@ -1003,7 +1003,7 @@ func (m *MsgMgo) GetLastMessage(ctx context.Context, conversationID string) (*mo
 		{
 			"$match": bson.M{
 				"doc_id": bson.M{
-					"$regex": fmt.Sprintf("^%s", conversationID),
+					"$regex": fmt.Sprintf("^%s:", conversationID),
 				},
 			},
 		},