diff --git a/lib/Doctrine/Record.php b/lib/Doctrine/Record.php
index b1d72200..ec9606ce 100644
--- a/lib/Doctrine/Record.php
+++ b/lib/Doctrine/Record.php
@@ -1526,6 +1526,12 @@ protected function _isValueModified($type, $old, $new)
             return true;
         }
 
+        if ($old === null && $new === self::$_null) {
+            return false;
+        }
+        if ($new === null && $old === self::$_null) {
+            return false;
+        }
         if ($type == 'boolean' && (is_bool($old) || is_numeric($old)) && (is_bool($new) || is_numeric($new)) && $old == $new) {
             return false;
         } else if (in_array($type, array('decimal', 'float')) && is_numeric($old) && is_numeric($new)) {