diff --git a/core/modules/file/src/Element/ManagedFile.php b/core/modules/file/src/Element/ManagedFile.php
index ca4e887a1b..0c7814149f 100644
--- a/core/modules/file/src/Element/ManagedFile.php
+++ b/core/modules/file/src/Element/ManagedFile.php
@@ -398,7 +398,8 @@ public static function preRenderManagedFile($element) {
    * Render API callback: Validates the managed_file element.
    */
   public static function validateManagedFile(&$element, FormStateInterface $form_state, &$complete_form) {
-    $clicked_button = end($form_state->getTriggeringElement()['#parents']);
+    $triggering_element = $form_state->getTriggeringElement();
+    $clicked_button = $triggering_element ? end($triggering_element['#parents']) : '';
     if ($clicked_button != 'remove_button' && !empty($element['fids']['#value'])) {
       $fids = $element['fids']['#value'];
       foreach ($fids as $fid) {