Hide Object in Hierarchy Window

I'm trying to make an object container which holds several game objects which aren't shown in the hierarchy window, but I can't seem to get the hideFlags property to work. Here's the script I currently have:

class ObjectContainerEditor extends Editor { function OnInspectorGUI() { if (GUILayout.Button("Create Object")) CreateObject(); }

 function CreateObject() {
     var newObj : GameObject = new GameObject();
     newObj.transform.parent = target.transform;

     newObj.hideFlags = HideFlags.HideInHierarchy;
 }

It adds a new GameObject to the target object like it's supposed to, but the new object is still shown in the hierarchy window. What am I doing wrong?