Shatterproof glass will be installed this year on the display windows in parts of the royal buildings of the Forbbiden City, or Palace Museum, the museum director said on Monday.

In May, a tourist damaged an ancient clock after breaking a window.

Shan Jixiang told Beijing News that more than 100 pieces of shatterproof glass will be installed at the display windows in the eastern six palaces and the western six palaces.

Shan said other windows that do not display ancient items will not get the new glass, “mainly to keep changes minimal to the exhibition of the historical relics” in the museum, since some of the windows are also centuries old.