diff --git a/index.html b/index.html
index 3e77ea6..ce618e6 100644
--- a/index.html
+++ b/index.html
@@ -1540,9 +1540,11 @@
 
         function updateUndoButton() {
             const btn = document.getElementById('undoBtn');
-            btn.textContent = undoStack.length > 0 ? `Undo (${undoStack.length})` : 'Undo';
-            btn.disabled = undoStack.length === 0;
-            btn.style.opacity = undoStack.length === 0 ? '0.5' : '1';
+            if (btn) {
+                btn.textContent = undoStack.length > 0 ? `Undo (${undoStack.length})` : 'Undo';
+                btn.disabled = undoStack.length === 0;
+                btn.style.opacity = undoStack.length === 0 ? '0.5' : '1';
+            }
         }
 
         // GPS functions