Remove type casting
diff --git a/system/database/drivers/pdo/pdo_result.php b/system/database/drivers/pdo/pdo_result.php
index 6bc923e..1c72216 100644
--- a/system/database/drivers/pdo/pdo_result.php
+++ b/system/database/drivers/pdo/pdo_result.php
@@ -196,7 +196,7 @@
 					}
 					else
 					{
-						$F->max_length	= ($field['len'] > 255) ? NULL : (string) $field['len'];
+						$F->max_length	= ($field['len'] > 255) ? 0 : $field['len'];
 						$F->primary_key = (int) ( ! empty($field['flags']) && in_array('primary_key', $field['flags']));
 					}