There is a separate system of control over alterations to buildings which are listed as being of architectural or historic interest ("listed buildings"). Alterations to such a building that affect its architectural or historic character, inside or outside, require "listed building consent" (and may also require planning permission if the scope of the proposed alterations or development is above that classified as permitted development). It is an offence to carry out works without the necessary listed building consent. The owner of a listed building can also be compelled to keep it in a good state of repair to safeguard its architectural or historic significance.