Following its arrival, it was found that parts of the Codex, including most of the Torah, had been lost. The Codex was entrusted to the keeping of the Ben-Zvi Institute and the Hebrew University of Jerusalem, though the Porat Yosef Yeshivah has argued that, as the spiritual heir of the Aleppo community, it was the legitimate guardian. Some time after the arrival of the Codex, Mordechai Breuer began the monumental work of reconstructing the lost sections, on the basis of other well-known ancient manuscripts.