gnome-disks can't create new partitions with gtk3-nocsd

[Laulajatar]

In gnome-disks, the window to create a new partition has 2 buttons in the header that don't get shown anywhere else when nocsd removes it.

Without gtk3-nocsd:

With gtk3-nocsd:

I'm on Manjaro with XFCE. The commit that caused it was c7e153f.
I tried using env GTK3NOCSD_SHOW_HEADER=1 ./gtk3-nocsd gnome-disks but it didn't help.