Just a few weeks after Istanbul’s former Hagia Sophia museum returned to its original status as a mosque, the Chora museum, also known as the Kariye mosque, is following suit.

The Chora dates back to the sixth-century Byzantine Empire, when it operated as a church. After Mehmet II conquered Istanbul in the 16th century it was converted into a mosque. In 1945, it was converted again, this time into a museum under the auspices of Turkey’s education ministry.

However, late last year, a Turkish court reversed the 1945 decision and, on August 21, Turkish president Recep Tayyip Erdoğan signed a decree ordering that “the management of the Kariye Mosque be transferred to the Religious Affairs Directorate, and (the mosque) opened to worship,” according to the Turkish news outlet TRT World.

Hagia Sophia, a former Greek Orthodox Christian cathedral, later an Ottoman mosque. Photo by Frank Bienewald/LightRocket via Getty Images.

Robert Ousterhout, a professor emeritus in art history at the University of Pennsylvania, called the move a “blatant attempt to erase Istanbul’s rich Byzantine heritage,” in the Art Newspaper.

Despite the proclamation in November, few believed the Kariye conversion would really happen, Ousterhout told Artnet News “Unlike Hagia Sophia, the Kariye never held a significant political position—it survived in obscurity through the Ottoman period and was falling down and all but abandoned when the restoration was undertaken in the 1940s,” he said. The new conversion is tantamount to “Erdogan thumbing his nose at the West,” Ousterhout added.

The move could endanger the Kariye’s 14th-century frescos and mosaics, which are regarded among the finest examples of Byzantine art in the world, earning it the nickname, the “Sistine Chapel of Byzantium.”

Meanwhile, in an article shared with Artnet News, for for the upcoming September edition of History Today, titled “Museum or Mosque,” Ousterhout says the Hagia Sophia “has been a monument to selective readings of history.”

The news comes as part of a long battle over the fate of historic buildings that have religious pasts. In recounting the conversion of other Turkish museums, including the Ayasofya in Iznik, to mosques, Ousterhout noted in a forthcoming article in History Today that “Reaction has been predictable: academics and secularists have decried the move, Islamists are delighted.”