diff --git a/lib/form/filepicker.php b/lib/form/filepicker.php
index 31a5329..dad4c6b 100644
--- a/lib/form/filepicker.php
+++ b/lib/form/filepicker.php
@@ -121,7 +121,7 @@ class MoodleQuickForm_filepicker extends HTML_QuickForm_input {
         }
 
         // make sure max one file is present and it is not too big
-        if (!is_null($draftitemid)) {
+        if (!is_null($draftitemid) && $draftitemid !== '') {
             $fs = get_file_storage();
             $usercontext = get_context_instance(CONTEXT_USER, $USER->id);
             if ($files = $fs->get_area_files($usercontext->id, 'user', 'draft', $draftitemid, 'id DESC', false)) {