diff --git a/kfet/static/kfet/js/history.js b/kfet/static/kfet/js/history.js
index 4c2a2664..57829a10 100644
--- a/kfet/static/kfet/js/history.js
+++ b/kfet/static/kfet/js/history.js
@@ -248,7 +248,7 @@ function KHistory(options = {}) {
                 that.cancel_entry(entry);
             }
             if (type == "operation") {
-                for (let opegroup of data["opegroups_to_update"]) {
+                for (let opegroup of (data["opegroups_to_update"] || [])) {
                     that.update_opegroup(opegroup)
                 }
             }