sites_database_user_add() not returning id

I am stuck trying to create a site through the remote api.
my version is ISPConfig 3.0.5.4p5
my code is basically

Code:

$dbUserParams = array(
    'server_id' => $serverID,
    'database_user' =>  $username,
    'database_password' => $password
);
$dbUserId = $this->client->sites_database_user_add($this->sessionId, $clientID, $dbUserParams);

This creates the user but does not return a value $dbUserID is not set

the user seems to not actually be created in mysql just added to the "web_database_user" table