USB mount problem

I have Alpine box on Fujitsu thin client. I plan to set-up samba server with external usb-hdd attached. My problem is that external usb-hdd (/dev/sdb, ext2) isn't mounted automatically. I tried to manually edit /etc/fstab to mount /dev/sdb1 on /mnt but it doesn't work.
When I issue simple mount command:
mount /dev/sdb1 /mnt
I get this error:
mount: mounting /dev/sdb1 on /mnt failed: Invalid argument

I also installed e2fsprogs to add ext2 extra support, also with no luck.

Please help, I am stuck on such simple problem.

Maciej