diff --git a/apps/timestamplog/interface.html b/apps/timestamplog/interface.html
index 6febe7849..b54dfb010 100644
--- a/apps/timestamplog/interface.html
+++ b/apps/timestamplog/interface.html
@@ -14,7 +14,7 @@
 
       function HTMLStampLog(stampLog) {
         html = ''
-        if (stampLog.length) {
+        if (stampLog !== undefined && stampLog.length) {
           html += '<ol>';
           for (const logItem of stampLog) {
             html += ('<li>' + new Date(logItem.stamp).toLocaleString() + '</li>');