ClangFormat misconverts Tab indentation from old settings

I have a C++ Style configuration that uses Tabs for indentation.

When .clang-format file is created for this configuration, it is created with UseTab: Never, and the lines are indented with spaces.

To reproduce:

qtcreator -settingspath /tmp/no-tabs -noload ClangFormat

Edit -> Preferences -> C++ -> Code Style
Copy Qt, change the Tab policy to Tabs Only, Apply and quit Qt Creator

Now run again with:

qtcreator -settingspath /tmp/no-tabs

Edit -> Preferences -> C++ -> Code Style

Notice that the preview appears with spaces, and if you scroll to the bottom (it's the last setting) you'll see UseTab: Never.

Now switch to General. The combobox shows Spaces Only, but the preview has tabs .

If you manually change it to Tabs Only, the issue is fixed.