diff --git a/htdocs/install/upgrade.php b/htdocs/install/upgrade.php
index 8f27c3d053e..56ad5714bef 100644
--- a/htdocs/install/upgrade.php
+++ b/htdocs/install/upgrade.php
@@ -170,7 +170,8 @@ if (isset($_GET["action"]) && $_GET["action"] == "upgrade")
                                         'DB_ERROR_KEY_NAME_ALREADY_EXISTS',
                                         'DB_ERROR_RECORD_ALREADY_EXISTS',
                                         'DB_ERROR_NOSUCHTABLE',
-                                        'DB_ERROR_NOSUCHFIELD'
+                                        'DB_ERROR_NOSUCHFIELD',
+                                        'DB_ERROR_CANNOT_CREATE'    // Qd contrainte deja existante
                                        );
                         if (in_array($errno,$okerror))
                         {