The Undo feature has been recognized as an important feature of collaborative systems. The Operational Transformation (OT) is a suitable approach to maintain consistency of shared documents. In all existing OT undo approaches, this feature is provided by the system without a specific design. In this paper, we argue that such feature could not always achieve the user's undo intention. Therefore, we propose a new generic and flexible undo framework called ``Compensation''. This framework allows defining an adequate modification to counterbalance any action performed by any user in the collaborative system.