Delete volume seems not work

[kladiv]

Hello,
really nice docker volume plugin for DOBS. I installed using --alias dostorage
After some tests , i tried to remove created volume, but it seems not work:

# docker volume ls
DRIVER              VOLUME NAME
...
dostorage:latest    test-volume

Error below:

# docker volume rm test-volume
Error response from daemon: unable to remove volume: remove mgob-volume: volume (internal) mgob-volume has no mountpoint

Then i forced, command seems work...

# docker volume rm test-volume --force
test-volume

but volume still present:

# docker volume ls
DRIVER              VOLUME NAME
dostorage:latest    test-volume

# docker volume inspect test-volume
[
    {
        "CreatedAt": "0001-01-01T00:00:00Z",
        "Driver": "dostorage:latest",
        "Labels": null,
        "Mountpoint": "/var/lib/docker/plugins/aa3bb7ec29ffde404324a048211c6d05cfaf3361e28ec50606aa14abb0be8b3c/rootfs",
        "Name": "test-volume",
        "Options": {},
        "Scope": "global"
    }
]

# ls -altr /var/lib/docker/plugins/aa3bb7ec29ffde404324a048211c6d05cfaf3361e28ec50606aa14abb0be8b3c/
total 20
drwx------  5 root root 4096 May  2 07:11 ..
drwxr-xr-x 19 root root 4096 May  2 07:11 rootfs
-rw-------  1 root root 1702 May  2 07:11 config.json
drwx------  4 root root 4096 May  2 07:11 .
drwxr-xr-x  3 root root 4096 May  2 07:31 propagated-mount

Can you check it please?
Thank you.