Chinese phone maker Vivo has made the X20 Plus UD official, the very first smartphone with an in-display fingerprint scanner. Although the phone’s best feature is highly sought after by many Android phone fans, it has one disadvantage: the in-display fingerprint sensor won’t work with thick screen protectors.

According to Engadget, some screen protectors will prevent the in-display fingerprint scanner on the Vivo X20 Plus UD from working. Screen protectors must not exceed a certain thickness if users want the fingerprint scanner to work correctly. When a screen protector is too thick, it may affect the fingerprint’s reflection on the optical fingerprint sensor.

To make sure that this issue is avoided, Vivo will be including its very own screen protector inside the X20 Plus UD’s box. It’s very likely that customers will have to buy replacement screen protectors from Vivo directly if they want to make sure that the in-display fingerprint scanner keeps working as intended.

Vivo X20 Plus UD The Vivo X20 Plus UD is now available to pre-order in China and it's scheduled to be released on Feb. 1. Photo: Vivo

Vivo is using Synaptics’ Clear ID optical fingerprint scanner on the X20 Plus UD. The Clear ID sensor is only able to work on devices that have OLED displays. The scanner uses a light sensor system that is able to read fingerprints by emitting light through the gaps between the OLED screen’s pixels. If a screen protector is too thick, it may hinder the fingerprint scanner from accurately identifying the user’s fingerprint as light is reflected back to the sensor.

The in-display fingerprint scanner on the Vivo X20 Plus UD may also not work when the display is scratched or damaged in the area where the scanner is placed, according to Phone Arena. This is also why a screen protector for the new phone is a must-have for all users.

The Vivo X20 Plus UD comes with a 6.43-inch full HD 18:9 OLED display. It’s also being powered by Qualcomm’s Snapdragon 635 processor with 4GB of RAM and 128GB of internal storage. The device also has a hybrid SIM slot that lets users put two SIM cards or one SIM card and one microSD card for expanded storage, accoridng to GSM Arena.

The device is also packing a dual-camera setup on its back. The main camera comes with a 12MP sensor with an f/1.8 aperture lens, while the secondary camera comes with a 5MP sensor. Up front, the handset features another 12MP camera that also comes with its own LED flash. Design-wise, the X20 Plus UD looks pretty similar to the OnePlus 5, as pointed out by 9To5Google.

The Vivo X20 Plus UD is now available to pre-order in China and starts at CNY3,598 (US$565). The phone will officially go on sale on Feb. 1 in the country. Vivo hasn’t given any information if the device will be released in other markets.