diff --git a/api.php b/api.php
index 46f534e..9cecb47 100644
--- a/api.php
+++ b/api.php
@@ -1072,7 +1072,7 @@ switch($request[0]) {
 				switch($request[2]){
 					/*	APIDOC: project/mentor/edit
 						post(mentors array of mentor arrays)
-						object(mentor: {id,registrations_id,firstname,lastname,email,phone,organization,position,description})
+						object(mentor: {id,firstname,lastname,email,phone,organization,position,description})
 						object(mentors: {mentor,...})
 						description(edit a list of project mentors or add new ones if a mentor array has no id)
 						return(mentors array of mentor arrays)
diff --git a/register_participants.inc.php b/register_participants.inc.php
index 16e7fdd..7b3fad5 100644
--- a/register_participants.inc.php
+++ b/register_participants.inc.php
@@ -609,7 +609,7 @@ function userCanEditMentor($userId, $mentorId){
 // return a list of fields that should be included in the mentor array
 function getMentorFields(){
 	return array(
-		'id', 'registrations_id', 
+		'id', 
 		'firstname', 'lastname', 
 		'email', 'phone', 
 		'organization', 'position', 
@@ -643,6 +643,7 @@ function saveMentorData($data){
 	$queryParts = array();
 	foreach($fields as $key){
 		if($key == 'id') continue;
+		if($key == 'registrations_id') continue;
 		$queryParts[] = "`$key` = '{$data[$key]}' ";
 	}
 	$query .= implode(',', $queryParts);