Index: moodle/mod/lamslesson/callback.php
===================================================================
diff -u -rc6f6605de18894e645f9a9cabb994996fdf90924 -r1fd4020ce4e418be139dbe743a0d4cfd3b67bd74
--- moodle/mod/lamslesson/callback.php	(.../callback.php)	(revision c6f6605de18894e645f9a9cabb994996fdf90924)
+++ moodle/mod/lamslesson/callback.php	(.../callback.php)	(revision 1fd4020ce4e418be139dbe743a0d4cfd3b67bd74)
@@ -48,4 +48,7 @@
 
 $gradebookmark = lamslesson_get_lams_outputs($user->username,$lamslesson,$user->username);
 
+// let LAMS know that mark retrieval process has finished successfully
+echo 'OK';
+
 ?>