Microsoft today accidentally released an internal-only version of Windows 10 to testers, revealing a new Start menu design. The software giant distributed Windows 10 build 18947, meant for internal Xbox development, to Windows Insider testers using 32-bit devices. It’s an internal-only build from the company’s canary branch, and yet Microsoft published it to all Windows 10 testers whether they’re in release preview, fast ring, or even slow ring testing. The build is no longer available.

Thankfully, it was only released to 32-bit systems, which aren’t widely used, but it’s an embarrassing mistake for Microsoft’s Windows 10 testing efforts. This internal build appears to include a new Start menu design, that’s very early in testing, without Microsoft’s Live Tiles. It’s something Microsoft is testing internally for Windows Lite, but it’s not clear whether Windows 10 will fully drop Live Tiles in the Start menu anytime soon. This new build also included a GIF search tool within the emoji picker for Windows 10.

This isn’t the first time Microsoft has made this mistake. Back in 2017, the company released internal versions of Windows 10 for PC and mobile, and caused some devices to enter a reboot loop. Microsoft quickly spotted the mistake, and helped affected Windows 10 users with a device recovery tool.

Microsoft’s Windows Insider chief, Dona Sarkar, said earlier today the company was “looking into” this latest issue. A company spokesperson later told The Verge, “This was an error and we’ve since pulled the build.”

Update 7/24, 5:02PM ET: Added comment from Microsoft.