From 9ba97c217dee9780fb2b94df752c05b50dab4bb9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jean-Fran=C3=A7ois=20Rivi=C3=A8re?=
 <jean-francois.riviere@openedition.org>
Date: Thu, 13 Dec 2018 21:42:18 +0100
Subject: [PATCH] fix check_issn hook (didn't work when the check digit=0)

---
 lodel/scripts/hookfunc.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lodel/scripts/hookfunc.php b/lodel/scripts/hookfunc.php
index 0f1d17d8a..8b367a956 100644
--- a/lodel/scripts/hookfunc.php
+++ b/lodel/scripts/hookfunc.php
@@ -73,7 +73,7 @@ function check_issn(&$context, $field, &$errors)
         }
 
         $check %= 11;
-        $check  = 11 - $check;
+        if ($check != 0) $check  = 11 - $check;
 
         if ($check == $checksum || (($check == 10) && ($checksum == 'X'))) {
             $context['data'][$field] = wordwrap($value,4,'-', true);