Stuck in loop of formatting a 91.5MiB volume

[kerneliusz]

I've started a fresh OS9 system and I keep getting this all the time:

I'm unable to proceed because the volume cannot be formatted in any way. Trying to eject it makes the formatting dialog come back within milliseconds. This dialog forces itself on top of everything else happening on the system.
Here's my /home/kerneliusz/.config/SheepShaver/prefs:

disk /home/kerneliusz/git/vcmi-demo/sheepshaver-disk/OS9.img
cdrom /dev/cdrom
extfs /
screen win/800/600
windowmodes 0
screenmodes 0
seriala /dev/ttyS0
serialb /dev/ttyS1
rom /home/kerneliusz/git/vcmi-demo/newworld86.rom
bootdrive 0
bootdriver 0
ramsize 134217728
frameskip 8
gfxaccel true
nocdrom false
nonet false
nosound false
nogui false
noclipconversion false
ignoresegv true
ignoreillegal true
jit true
jit68k false
keyboardtype 5
hardcursor false
hotkey 0
scale_nearest false
scale_integer false
cpuclock 0
yearofs 0
dayofs 0
mag_rate 0
swap_opt_cmd true
sound_buffer 0
name_encoding 0
keycodes false
mousewheelmode 1
mousewheellines 3
dsp /dev/dsp
mixer /dev/mixer
idlewait true
sdlrender software

Log:

SheepShaver V2.5 by Christian Bauer and Mar"c" Hellwig
Gtk-Message: 17:23:58.790: Failed to load module "canberra-gtk-module"
Using prefs file at /home/kerneliusz/.config/SheepShaver/prefs
Reading ROM file...
Using SDL/pulseaudio audio output
Using SDL_Renderer driver: software
Detected CPU features: MMX SSE SSE2 SSE3 SSSE3
PowerPC CPU emulator by Gwenole Beauchesne
WARNING: Unknown DiskStatus(6)

[Deleted user]

I've figured this out!

cdrom /dev/cdrom

I had a CD in my CD drive that has exactly 91.5MB recorded onto it. Completely unrelated to OS9.
In order to make it work, I had to eject the CD entirely, not just unmount it.