'Create patch' does not work for newly added files (even when staged)

[MartijnPW]

I'm trying to create a patch from my working copy changes. 

For some reason, only the modified files show up in the UI where you can select the files.

According to other posted suggestions, it should work when the added files have been staged... But for me it doesn't. 

Here you can see that in the regular window, you see 6 modified and 8 added files:

But in the 'Create Patch' UI, only the 6 modified files show up:

I'm using 3.4.18 on Windows, with the following Git settings:

Any help is more than welcome!

Martijn