diff --git a/core/model/DataObject.php b/core/model/DataObject.php
index bee4f95cb..c564c3c1c 100644
--- a/core/model/DataObject.php
+++ b/core/model/DataObject.php
@@ -2651,6 +2651,11 @@ class DataObject extends ViewableData implements DataObjectInterface {
 	 * Inserts standard column-values when a DataObject
 	 * is instanciated. Does not insert default records {@see $default_records}.
 	 * This is a map from classname to default value.
+	 * 
+	 *  - If you would like to change a default value in a sub-class, just specify it.
+	 *  - If you would like to disable the default value given by a parent class, set the default value to 0,'',or false in your
+	 *    subclass.  Setting it to null won't work.
+	 * 
 	 * @var array
 	 */
 	public static $defaults = null;