Storyboard does not load anymore after upgrading Xcode to version 9.1 (9B55)

After the update of Xcode to build 9b55 this morning my storyboard did not load anymore.

Xcode is too new
'This file has been edited in a version of Xcode which is unsupported by the designer. Documents saved in Xcode 9.1 format, or older, are supported.'

I did not even open the storyboard in Xcode Designer... I use the alfa channel 7.3 Build 708 of Visual Studio.
Is there anything that I can change in the XML of the storyboard to make it open in Visual Studio again ?

The storyboard starts with :

<?xml version="1.0" encoding="UTF-8"?>

Would lowering the toolsVersion work ? If so, what would be a "good" version ?

Thanks

Bert