diff --git a/htdocs/install/etape1.php b/htdocs/install/etape1.php
index b4ba5179b8a..4002605b51c 100644
--- a/htdocs/install/etape1.php
+++ b/htdocs/install/etape1.php
@@ -134,7 +134,7 @@ if ($_POST["action"] == "set")
     
             if (file_exists("$conffile"))
             {
-                include ("$conffile");
+                include_once("$conffile");
                 print "<tr><td>".$langs->trans("ConfigurationSaving")."</td><td>".$langs->trans("OK")."</td>";
             }
             else
@@ -153,7 +153,7 @@ if ($_POST["action"] == "set")
         }
 
         // Chargement driver acces bases
-        include_once("../lib/databases/".$dolibarr_main_db_type.".lib.php");
+        require_once($dolibarr_main_document_root."/lib/databases/".$dolibarr_main_db_type.".lib.php");
 
     }
 
diff --git a/htdocs/install/etape5.php b/htdocs/install/etape5.php
index 220317d755b..52c49e0896b 100644
--- a/htdocs/install/etape5.php
+++ b/htdocs/install/etape5.php
@@ -29,11 +29,6 @@
 */
 
 include_once("./inc.php");
-if (file_exists($conffile)) include_once($conffile);
-if (! isset($dolibarr_main_db_prefix) || ! $dolibarr_main_db_prefix) $dolibarr_main_db_prefix='llx_'; 
-define('MAIN_DB_PREFIX',$dolibarr_main_db_prefix);
-require_once($dolibarr_main_document_root . "/lib/databases/".$dolibarr_main_db_type.".lib.php");
-require_once($dolibarr_main_document_root . "/conf/conf.class.php");
 
 $setuplang=isset($_POST["selectlang"])?$_POST["selectlang"]:(isset($_GET["selectlang"])?$_GET["selectlang"]:'auto');
 $langs->setDefaultLang($setuplang);
@@ -82,7 +77,6 @@ if ($_POST["action"] == "set" || $_POST["action"] == "upgrade")
     print '<table cellspacing="0" cellpadding="2" width="100%">';
     $error=0;
 
-    $conf = new Conf();
     $conf->db->type = $dolibarr_main_db_type;
     $conf->db->host = $dolibarr_main_db_host;
     $conf->db->name = $dolibarr_main_db_name;
diff --git a/htdocs/install/fileconf.php b/htdocs/install/fileconf.php
index c3517770ddd..52d383c4615 100644
--- a/htdocs/install/fileconf.php
+++ b/htdocs/install/fileconf.php
@@ -42,8 +42,6 @@ $langs->load("install");
 
 pHeader($langs->trans("ConfigurationFile"),"etape1");
 
-// Ici, le fichier conf.php existe et est forcément editable car le test a été fait précédemment.
-include_once($conffile);
 
 print '<table border="0" cellpadding="1" cellspacing="0">';
 
diff --git a/htdocs/install/inc.php b/htdocs/install/inc.php
index 8aa4cdc01a5..a75ecb9194c 100644
--- a/htdocs/install/inc.php
+++ b/htdocs/install/inc.php
@@ -29,9 +29,17 @@
 require_once('../translate.class.php');
 require_once('../lib/functions.inc.php');
 
-
-$docurl = '<a href="doc/dolibarr-install.html">documentation</a>';
 $conffile = "../conf/conf.php";
+if (file_exists($conffile))
+{
+	include_once($conffile);
+	require_once($dolibarr_main_document_root . "/conf/conf.class.php");
+	require_once($dolibarr_main_document_root . "/lib/databases/".$dolibarr_main_db_type.".lib.php");
+	$conf=new Conf();
+}
+if (! isset($dolibarr_main_db_prefix) || ! $dolibarr_main_db_prefix) $dolibarr_main_db_prefix='llx_'; 
+define('MAIN_DB_PREFIX',$dolibarr_main_db_prefix);
+
 
 define('DOL_DOCUMENT_ROOT','../');