Meta Platforms’ Oculus virtual reality headsets are a vital step toward creating what its CEO, Mark Zuckerberg, calls the metaverse, an immersive internet in which people can interact in digital spaces. In addition to building Oculus, Meta has acquired at least six companies that made some of the most popular games and other apps for the headsets—including, most recently, the developer of Supernatural, a VR fitness app that became a breakout hit. Meta says by owning the apps, it can pour more money into them and create better VR experiences.

Meta’s first five VR app acquisitions went through without a hitch because they were too small to trigger a cursory review by U.S. antitrust regulators. But those regulators are slowing down the $400 million-plus Supernatural deal, according to two people with knowledge of the situation. Shortly after Thanksgiving, the Federal Trade Commission opened an in-depth probe of the acquisition, meaning Meta may not be able to finalize the acquisition for another year, assuming the agency doesn’t formally challenge the deal in court, causing additional delays.