It's pretty much a case of copy/paste the commands (the beauty of CLI). So I would suspect that something is not quite right in your PVE install. Did you install from a 1.9 ISO, or did you update from an earlier ISO install, or did you install on top of Debian? Probably the first thing I'd try is to make sure that you have everything up to date. See here (it details upgrading to 1.9 from an earlier release, but should still apply in your instance).
I don't think you can do anything 'wrong'
It's pretty much a case of copy/paste the commands (the beauty of CLI). So I would suspect that something is not quite right in your PVE install. Did you install from a 1.9 ISO, or did you update from an earlier ISO install, or did you install on top of Debian? Probably the first thing I'd try is to make sure that you have everything up to date. See here (it details upgrading to 1.9 from an earlier release, but should still apply in your instance).