diff --git a/system/database/DB_driver.php b/system/database/DB_driver.php
index 1e5e8c6..2679139 100644
--- a/system/database/DB_driver.php
+++ b/system/database/DB_driver.php
@@ -993,7 +993,7 @@
 		{
 			return ($str === FALSE) ? 0 : 1;
 		}
-		elseif (is_null($str))
+		elseif ($str === NULL)
 		{
 			return 'NULL';
 		}