diff --git a/htdocs/main.inc.php b/htdocs/main.inc.php
index c968b4da053..58ef723f135 100644
--- a/htdocs/main.inc.php
+++ b/htdocs/main.inc.php
@@ -30,7 +30,7 @@
  */
 
 @ini_set('memory_limit', '64M');	// This may be useless if memory is hard limited by your PHP
-define(DOL_DOCUMENT_ROOT_ALT,0);	// Set to 1 for extra custom path (for dev only)
+define(DOL_DOCUMENT_ROOT_ALT,0);	// Set extra custom path, ex: /path/to/htdocs/custom (for dev only)
 
 // For optionnal tuning. Enabled if environment variable DOL_TUNING is defined.
 // A call first. Is the equivalent function dol_microtime_float not yet loaded.