rbenv install wants a version number

I've been following along with the instructions at https://docs.joinmastodon.org/admin/install/, and everything seems to be going pretty well, until I get to the step ``` RUBY_CONFIGURE_OPTS=--with-jemalloc rbenv install ``` This results in ``` mastodon@saff-mastodon-1:~$ RUBY_CONFIGURE_OPTS=--with-jemalloc rbenv install Usage: rbenv install [-f|-s] [-kpv] <version> [-- <configure-args...>] rbenv install [-f|-s] [-kpv] <definition-file> rbenv install --list rbenv install --version -l, --list List latest stable versions for each Ruby -L, --list-all List all local versions, including outdated ones -f, --force Allow overwriting an existing installed version -s, --skip-existing Avoid overwriting an existing installed version ruby-build options: -v, --verbose Verbose mode: forward all build output to stdout/stderr -p, --patch Apply a patch from stdin before building -k, --keep Keep source tree in RBENV_BUILD_ROOT after installation (defaults to "RBENV_ROOT/sources") --version Show version of ruby-build For detailed information on installing Ruby versions with ruby-build, including a list of environment variables for adjusting compilation, see: https://github.com/rbenv/ruby-build#usage ``` Is it intended not to supply a version number? If it helps: ``` mastodon@saff-mastodon-1:~$ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 24.04.3 LTS Release: 24.04 Codename: noble ```