diff --git a/htdocs/product/canvas/product.livre.class.php b/htdocs/product/canvas/product.livre.class.php
index f5c644f95a3..26bd583969a 100644
--- a/htdocs/product/canvas/product.livre.class.php
+++ b/htdocs/product/canvas/product.livre.class.php
@@ -262,7 +262,7 @@ class ProductLivre extends Product
 	$sum += 3 * $ean{$i};
       }
 
-    $key = ($sum % 10);
+    $key = (10 - ($sum % 10));
 
     return $key;
   }