The mosque is not rectangular, however, because of the constraints of urban construction.[6] Specifically, the northeastern corner was built so that it would not encroach upon Tabanna Street nor a neighboring small lane.[7] It is not, however, as irregular as some mosques in urban Cairo, such as Ulmas' Mosque. Notably, the only reference for the start of construction comes from the foundation: a band of inscription at the mosque's west entrance suggests that the mosque went under construction in 739/1338–9.[3]