diff --git a/classes/sprig/field/nativetimestamp.php b/classes/sprig/field/nativetimestamp.php
old mode 100644
new mode 100755
index 9a91b59..2ce53fa
--- a/classes/sprig/field/nativetimestamp.php
+++ b/classes/sprig/field/nativetimestamp.php
@@ -4,6 +4,7 @@
  *
  * @package    Sprig
  * @author     Marcus Cobden
+ * @author     Tomasz Jaskowski
  * @copyright  (c) 2010 Marcus Cobden
  * @license    MIT
  */
@@ -11,7 +12,11 @@ class Sprig_Field_NativeTimestamp extends Sprig_Field_Timestamp {
 
 	public function _database_wrap($value)
 	{
-		return new Database_Expression('FROM_UNIXTIME('. (int) $value . ')');
+		if ($value === null) {
+            return new Database_Expression('NULL');
+        } else {
+            return new Database_Expression('FROM_UNIXTIME('. (int) $value . ')');
+        }
 	}
 	
 	public function _database_unwrap($value)