COLUMBUS (WCMH) — FaceApp, a phone application that edits users’ photos, has apologized for a “hotness” filter that lightens skin tones on the photos.

The app can morph a photo into looking older, younger, more masculine or feminine, and several other options. It has been out for several months, but is becoming more popular in the United States.

Yaroslav Goncharov, the creator and CEO of the app, apologized and said the issue is with the app’s tech.

“We are deeply sorry for this unquestionably serious issue,” Goncharov told the Guardian in a statement. “It is an unfortunate side-effect of the underlying neural network caused by the training set bias, not intended behaviour.”