diff --git a/booking.studygroups.inc b/booking.studygroups.inc
index 579d166..69031aa 100644
--- a/booking.studygroups.inc
+++ b/booking.studygroups.inc
@@ -910,7 +910,7 @@ function _booking_studygroups_update_preallocate($group, $group_mapping, &$sessi
 				_booking_assign_attendee_group($person->booking_node_id, $session_id, $gender, $age, $working_list, $session_count, $calculation_messages);
 
 				//check if there is someone that should be allocated to a different group than this person
-				if (keep_separate_id > 0) {
+				if ($keep_separate_id > 0) {
 					//work out the next session to assign the other person to
 					$next_session = ($session_id % $group->booking_num_group_sessions) + 1;