diff --git a/booking.studygroups_report.inc b/booking.studygroups_report.inc
index 48a0b27..67cfb1d 100644
--- a/booking.studygroups_report.inc
+++ b/booking.studygroups_report.inc
@@ -40,7 +40,7 @@ function booking_studygroups_csv_report($group_id) {
   //get the list of study group session memberships
 	$session_members_query = db_query("SELECT m.*, p.* FROM {booking_studygroup_mapping} m
 		inner join {booking_person} p on p.nid = m.booking_node_id
-		WHERE m.booking_studygroup_id = :sid ORDER BY m.booking_session_id, m.booking_studygroup_role DESC", 
+		WHERE m.booking_studygroup_id = :sid ORDER BY m.booking_session_id, m.booking_studygroup_role DESC, p.booking_lastname", 
 		array(':sid' => $group_id));
   $session_members = $session_members_query->fetchAll();