Microsoft has pushed out a new Windows 10 Mobile preview build. The software giant announced Tuesday that build 10136 was now available for download for Windows Insider fast ring users. But there is a catch. Only fast ring users with their devices running Windows Phone 8.1 will be able to download it due to a migration bug.

Windows 10 Mobile Preview Build 10136 Released With Improved Cortana

Windows 10 shows some love for phablet users

That means fast ring users running the previous build 10080 will have to reset to Windows Phone 8.1 using the Windows Phone Recovery tool before they can install the newest build. Users running the build 10080 who decided not to go back to Windows Phone 8.1 will not get this build, but they will be getting the future builds when released.

Improvements in the new build suggest that Microsoft is taking mobile very, very seriously. It brings a lot of design improvements along with refined Cortana and Photos apps. Microsoft executive Gabriel Aul said that the improved Cortana is “very close” to its final design. The digital voice assistant can now track packages and flights. It will also get answers for questions, currency information, stock quotes, and weather.

Windows 10 Mobile build 10136 has a one-handed mode for phablets. It works pretty much like the one-handed mode on Apple’s iPhone 6 and 6 Plus. If you use a 5-inch or bigger smartphone, simply press and hold the start button and “your screen will slide down so you can reach items at the top of your screen.” The screen will return to normal once you repeat the same action or tap the blank space at the top.

Photos and camera apps get improvements

The Photos app boasts of several reliability and performance improvements. It now lets users quickly access their past photos. If you tap on a month, you’ll get a list of months to jump to images from a specific month. There are also some smaller changes such as font and icon changes, refined UI elements, and performance improvements to the camera app.

Windows 10 for PCs and tablets will start rolling out on July 29th. However, Microsoft hasn’t yet announced when the mobile version would arrive.