Redmine

Hi,
I'm new to redmine so please excuse if this question is stupid.
Committing with svn with closes, refs, etc. did not show up in redmine.
Although I checkted 'Changesets automatisch abrufen' in the administration panel.
So I tried
rake -f /path/to/redmine/Rakefile RAILS_ENV=production redmine:fetch_changesets
as mentioned in the wiki.
But I always get:

rake aborted!
Don't know how to build task 'redmine:fetch_changesets'
/usr/lib/ruby/vendor_ruby/rake/task_manager.rb:49:in `[]'
/usr/lib/ruby/vendor_ruby/rake/application.rb:115:in `invoke_task'
/usr/lib/ruby/vendor_ruby/rake/application.rb:94:in `top_level'
/usr/lib/ruby/vendor_ruby/rake/application.rb:94:in `each'
/usr/lib/ruby/vendor_ruby/rake/application.rb:94:in `top_level'
/usr/lib/ruby/vendor_ruby/rake/application.rb:133:in `standard_exception_handling'
/usr/lib/ruby/vendor_ruby/rake/application.rb:88:in `top_level'
/usr/lib/ruby/vendor_ruby/rake/application.rb:66:in `run'
/usr/lib/ruby/vendor_ruby/rake/application.rb:133:in `standard_exception_handling'
/usr/lib/ruby/vendor_ruby/rake/application.rb:63:in `run'
/usr/bin/rake:27

So I wonder what is going wrong here.
Thanks!

Environment:
Redmine version 2.3.3.stable
Ruby version 1.8.7-p352 (2011-06-30) [i686-linux]
Rails version 3.2.13
Environment production
Database adapter MySQL
Redmine plugins:
no plugin installed