diff --git a/kernel/model/export.go b/kernel/model/export.go
index 01b9ff466..b6dba1430 100644
--- a/kernel/model/export.go
+++ b/kernel/model/export.go
@@ -631,6 +631,7 @@ func prepareExportTree(bt *treenode.BlockTree) (ret *parse.Tree) {
 	ret.Path = bt.Path
 	ret.HPath = bt.HPath
 	ret.Box = bt.BoxID
+	ret.ID = bt.RootID
 	return
 }