diff --git a/htdocs/install/inc.php b/htdocs/install/inc.php
index 03ed96f7bb9..bf2e44042f3 100644
--- a/htdocs/install/inc.php
+++ b/htdocs/install/inc.php
@@ -116,9 +116,9 @@ if (! isset($conf->db->user)) $conf->db->user='';
 $conf->syslog->enabled=1;
 $conf->global->SYSLOG_LEVEL=constant('LOG_DEBUG');
 if (@is_writable('/tmp')) define('SYSLOG_FILE','/tmp/dolibarr_install.log');
-else if (isset($_ENV["TMP"]) && is_writable($_ENV["TMP"]))   define('SYSLOG_FILE',$_ENV["TMP"].'/dolibarr_install.log');
-else if (isset($_ENV["TEMP"]) && is_writable($_ENV["TEMP"])) define('SYSLOG_FILE',$_ENV["TEMP"].'/dolibarr_install.log');
-else define('SYSLOG_FILE','/dolibarr_install.log');
+else if (! empty($_ENV["TMP"])  && @is_writable($_ENV["TMP"]))  define('SYSLOG_FILE',$_ENV["TMP"].'/dolibarr_install.log');
+else if (! empty($_ENV["TEMP"]) && @is_writable($_ENV["TEMP"])) define('SYSLOG_FILE',$_ENV["TEMP"].'/dolibarr_install.log');
+else if (@is_writable("/")) define('SYSLOG_FILE','/dolibarr_install.log');
 define('SYSLOG_FILE_NO_ERROR',1);