Unknown flag --repository-file

I tired to backup my home directory with a command like
restic backup -v --repository-file /path/to/repo.txt --password-file /path/to/password.txt /home/username
The repo.txt contains something like sftp:user@remotehost:/path/to/restic_repo and password.txt contains the password.
Instead of starting the backup I get the unknown flag --repository-file error.
When I use the -r parameter it works fine.
What am I doing wrong?

The --repository-file flag was added with restic v0.11.0. Which version are you using (output of restic version)?

0.9.6

So apparently ubuntu gives you quite an old version with apt-get install restic, but restic self-update fixed that.