diff --git a/manage/import-export.js b/manage/import-export.js
index 2605e0a5..1a2f1d15 100644
--- a/manage/import-export.js
+++ b/manage/import-export.js
@@ -161,7 +161,7 @@ function importFromString(jsonString) {
       if (sameStyle(byId, item)) {
         oldStyle = byId;
       } else {
-        item.id = null;
+        delete item.id;
       }
     }
     if (!oldStyle && byName) {