diff --git a/lib/form/filemanager.php b/lib/form/filemanager.php
index 26c2271e0d4..af191a0e8d6 100644
--- a/lib/form/filemanager.php
+++ b/lib/form/filemanager.php
@@ -320,11 +320,15 @@ class MoodleQuickForm_filemanager extends HTML_QuickForm_element implements temp
     /**
      * Check that all files have the allowed type.
      *
-     * @param array $value Draft item id with the uploaded files.
+     * @param int $value Draft item id with the uploaded files.
      * @return string|null Validation error message or null.
      */
     public function validateSubmitValue($value) {
 
+        if (empty($value)) {
+            return;
+        }
+
         $filetypesutil = new \core_form\filetypes_util();
         $whitelist = $filetypesutil->normalize_file_types($this->_options['accepted_types']);