In their monograph "A skeletal revision of "Nepenthes" (Nepenthaceae)", published in 1997, Matthew Jebb and Martin Cheek identified three specimens belonging to "N. ovata" as "N. densiflora". One of these specimens, "Frey-Wyssling 43", was collected on Mount Pangulubao at 1800 m, which is the type locality of "N. ovata". It consists of an immature rosette and a lower pitcher. A second specimen, "Frey-Wyssling 13", was collected in Dolok "Baros", also at 1800 m. Finally, "Opperhout" 27/11/1929 was taken on that date from the summit of Dolok Sempenan at 1600 m. It consists of a rosette and a lower pitcher with its lid missing. Despite this, it can be identified as belonging to "N. ovata" based on the structure of the peristome. All three specimens are deposited at the Bogor Botanical Gardens (formerly the Herbarium of the Buitenzorg Botanic Gardens) in Java.