The fitness tracker device, Xiaomi Mi Band2, apparently does not work on people of color, according to tech blog Phandroid. Many dark-skinned users said the device cannot depict their heart rate sensor --- unless if it’s put on a lighter area of the body.

“Put a white paper below the sensor and it will work again,” a user suggested from the forum, "Mi Band 2 Heart Rate measure not working on Black People.”

Users with fairer skin have not seemed to face any mishaps compared to those who are darker. “Heart Rate measure is not working on Black skin, but when it kept in the palm, it is working fine. Please resolve this issue quickly,” another user states.

The device, which is known to give time, calculate one’s step, and show a person’s heart rate, has been at odds with dark-skinned users since October 2016 and many are still having difficulties with the impaired device.

“It is so frustrating, I'm facing same issue in the same conditions. If I put my finger in the sensor directly it works like a charm, however on my wrist doesn't,” user rmandhare wrote.

 Some users have even tried the device on more than one individual.

“Mi band 2 heart rate sensor not working in dark skin people, tried on different people," a user wrote.

Xiaomi, which released the device on June 7, did not return an email for comment from the International Business Times.

Apart from the skin color concerns, other users have complained the low-cost device is far from perfect. "The rubber bracelet is a topic of contention. I wore mine tight at first, hoping for accurate heart rate read-outs. But after half a day in Hong Kong’s humidity, my wrist began itching quite badly," wrote a reviewer for the South China Morning Post in July."I like the design of the metal clasp: a simple but secure pin and hole arrangement. Sadly though, it scrapes on the desk, picking up bits of paint. To avoid the issue, I wore it so that the module was on the inside of my wrist but that caused issues as it kept hitting the desk while I was typing."