Texture Pack Locked

If a texture pack is applied to a specific world, removing it from the world does not take effect. If I have the natural texture pack applied to a map and then remove it, I will receive a notification that it has been removed. However, once I load the world the natural texture pack is still applied. If I remove the natural texture pack and apply the classic texture pack, the classic texture pack will apply. Currently there is no way to play with the default texture pack if another pack has been applied. It appears to be locked since the 26.40 update.