Windows Phone 8.1 users looking forward to an upgrade to Windows 10 in December are going to be disappointed. After company representatives said in October that Windows 10 mobile upgrades would start sometime this month, Microsoft is now saying it won’t happen until early 2016.

“The Windows 10 Mobile upgrade will begin rolling out early next year to select existing Windows 8 and 8.1 phones,” a Microsoft spokesperson recently told ZDNet’s Mary Jo Foley.

Microsoft released the first Windows 10 phones in November with the launch of the Lumia 950 and 950 XL, but many users with Windows 8.1 phones are also being promised an upgrade to Microsoft’s latest and greatest.

At this writing Microsoft has yet to issue a complete list of Lumia devices slated for a Windows 10 bump. The first devices in line for Windows 10 include the Lumia 430, Lumia 435, Lumia 532, Lumia 535, Lumia 540, Lumia 635 (1GB RAM), Lumia 640, Lumia 640 XL, Lumia 735, Lumia 830, and Lumia 930.

There should be more handsets to come, as any device with the Lumia Denim update and more than 8GB of internal memory should be able to handle Windows 10.

The story behind the story: It’s not all bad news in the world of Windows 10 mobile. Earlier in December, Microsoft hit a significant milestone when all PCs and phones on the Insider program received the same Windows 10 build. That allows Microsoft to deliver timely updates to PCs and mobile devices at the same time. Not only will synchronized updates keep every Windows 10 device current with the same software (with obvious adjustments for each device type), but new features that further integrate phones and PCs can roll out to both Windows desktops and mobile handsets at the same time.