Abstract: A device for locking at least a door element in an opening to a space. The device includes a locking mechanism including a locking bar located on the inside of the door element. A protective housing includes a first part attached to the inside of the door element and a second part attached to an inside of an adjacent element. A protective plate is attached on the inside of the door element in a position such that the protective plate covers a gap between the door element and the adjacent element in connection with the extension of the locking bar over the gap when the locking bar is in a locked position. The parts of the protective housing are designed such that a gap between the parts of the protective housing does not coincide with the gap between the door element and the adjacent element.