diff --git a/login.php b/login.php
index 4b6fd67..5aed14f 100644
--- a/login.php
+++ b/login.php
@@ -138,10 +138,11 @@ function truncate_user($userobj) {
 
         } else if ($DB->record_exists('user', array('idnumber'=>$idnumber))) { // matched user by existing idnumber
 			if ($updatefields) {
-				$updateuser = get_complete_user_data('username', $username);
+				$updateuser = get_complete_user_data('idnumber', $idnumber);
 				$updateuser->email = $email;
 				$updateuser->firstname = $firstname;
 				$updateuser->lastname = $lastname;
+				$updateuser->username = $username;
 
 				// make sure we haven't exceeded any field limits
 				$updateuser = truncate_user($updateuser);