This viral video, uploaded to YouTube in September, shows an automatic soap dispenser at an Atlanta hotel failing to work when a black man places his hands under the nozzle. When his white friend does the same, however, the nozzle dispenses foamy soap into the man’s palm.

Although there’s humor to the video, it exposes a glaring flaw in how modern technology favors lighter skin. Here’s how the dispenser works: An infrared beam shoots out from an LED just under the nozzle, and in order to trigger the dispenser, the beam has to be reflected back to the sensor. If light is absorbed, the soap is never dispensed. That’s what happens when someone with darker skin puts their hand under the nozzle; on the contrary, lighter skin reflects the LED beam more easily. To avoid these kinds of problems, companies should test their technology on a variety of skin tones.