diff --git a/system/database/DB_forge.php b/system/database/DB_forge.php
index 111546e..2dd243c 100644
--- a/system/database/DB_forge.php
+++ b/system/database/DB_forge.php
@@ -929,7 +929,7 @@
 				$field['default'] = empty($this->_null) ? '' : $this->_default.$this->_null;
 
 				// Override the NULL attribute if that's our default
-				$attributes['NULL'] = NULL;
+				$attributes['NULL'] = TRUE;
 				$field['null'] = empty($this->_null) ? '' : ' '.$this->_null;
 			}
 			else