Mosaics depicting Christian figures in Istanbul’s ancient Hagia Sophia will be covered with curtains during Muslim prayers, Turkish presidential spokesman Ibrahim Kalin said, as work to prepare the building for use as a mosque continues.

Authorities had said last week that the mosaics would be concealed with either curtains or lasers when the first prayers are held next Friday.

President Tayyip Erdogan declared Hagia Sophia open to Muslim worship earlier this month following a court ruling that said the building’s conversion to a museum in 1934 was unlawful.

Hagia Sophia dates back to the sixth century and has a history as both a church and a mosque before it was turned into a museum.