diff --git a/index.php b/index.php
index e368af9..0b851f7 100755
--- a/index.php
+++ b/index.php
@@ -166,7 +166,7 @@
 
         }
         // close the database connection
-        $db = NULL;
+        $db = null;
     }
     catch(PDOException $e)
     {