diff --git a/bureau/class/db_mysql.php b/bureau/class/db_mysql.php
index 7bf09c8e..b8cd8a65 100644
--- a/bureau/class/db_mysql.php
+++ b/bureau/class/db_mysql.php
@@ -37,8 +37,8 @@ class DB_Sql {
   
 
   /* PDO related variables */
-  private $pdo_instance = FALSE;
-  private $pdo_query = FALSE;
+  private $pdo_instance = NULL;
+  private $pdo_query = NULL;
 
   /**
    * Constructor