Yet another reason to rethink getting that sleeve tattoo. Users on Reddit and Twitter have begun reporting that the newly released Apple Watch does not work efficiently on a tattooed wrist. The ink seems to mess with the sensor that gauges heart rate and detection that the watch is actually on the users wrist. This becomes a huge problem since the Apple Watch requires users to enter a pin immediately after it detects that it left the user’s wrist.

iMore has already conducted tests and found that the Apple Watch brings significant issues for users with tattoos on their wrists.

Dark, solid colors seem to give the sensor the most trouble — our tests on solid black and red initially produced heart rate misreadings of up to 196 BPM before failing to read skin contact entirely.

The tests found that tattoos with lighter colors gave Apple Watch less trouble, and only effected the heart rate functionality.

The functionality is explained as follows:

Blood is red because it reflects red light and absorbs green light. Apple Watch uses green LED lights paired with light‑sensitive photodiodes to detect the amount of blood flowing through your wrist at any given moment. When your heart beats, the blood flow in your wrist — and the green light absorption — is greater. Between beats, it’s less. By flashing its LED lights hundreds of times per second, Apple Watch can calculate the number of times the heart beats each minute — your heart rate.

This technology is identical to other fitness bands in the industry such as Fitbit’s Charge HR and the Microsoft Band.

You can pick up an Apple Watch via Apple. Prices start at $349 and shipping can take up to 2 months depending on the model desired.