diff --git a/webservice/upload.php b/webservice/upload.php
index 03503b274db..619bb37e4bb 100644
--- a/webservice/upload.php
+++ b/webservice/upload.php
@@ -66,7 +66,12 @@ if ($fileuploaddisabled) {
 
 // check the user can manage his own files (can upload)
 $context = context_user::instance($USER->id);
-require_capability('moodle/user:manageownfiles', $context);
+
+// Allow allways to upload files to the draft area, no matter if the user can't manage his own files.
+// Files required by other webservices (like mod_assign ones) must be uploaded to the draft area.
+if ($filearea === 'private') {
+    require_capability('moodle/user:manageownfiles', $context);
+}
 
 if ($filearea !== 'private' and $filearea !== 'draft') {
     // Do not dare to allow more areas here!