diff --git a/core/modules/file/tests/file_test/src/Form/FileTestSaveUploadFromForm.php b/core/modules/file/tests/file_test/src/Form/FileTestSaveUploadFromForm.php
index 97cd9505fc..8bf72431a0 100644
--- a/core/modules/file/tests/file_test/src/Form/FileTestSaveUploadFromForm.php
+++ b/core/modules/file/tests/file_test/src/Form/FileTestSaveUploadFromForm.php
@@ -143,9 +143,11 @@ public function validateForm(array &$form, FormStateInterface $form_state) {
     $form['file_test_upload']['#upload_validators'] = $validators;
     $form['file_test_upload']['#upload_location'] = $destination;
 
-    drupal_set_message($this->t('Number of error messages before _file_save_upload_from_form(): @count.', ['@count' => count(drupal_get_messages('error', FALSE))]));
+    $beforeMessages = drupal_get_messages('error', FALSE);
+    drupal_set_message($this->t('Number of error messages before _file_save_upload_from_form(): @count.', ['@count' => isset($beforeMessages['error']) ? count($beforeMessages['error']) : 0]));
     $file = _file_save_upload_from_form($form['file_test_upload'], $form_state, 0, $form_state->getValue('file_test_replace'));
-    drupal_set_message($this->t('Number of error messages after _file_save_upload_from_form(): @count.', ['@count' => count(drupal_get_messages('error', FALSE))]));
+    $afterMessages = drupal_get_messages('error', FALSE);
+    drupal_set_message($this->t('Number of error messages after _file_save_upload_from_form(): @count.', ['@count' => isset($afterMessages['error']) ? count($afterMessages['error']) : 0]));
 
     if ($file) {
       $form_state->setValue('file_test_upload', $file);