web-console: Return key not working

I created an empty Rails 4.2 application using rails new. I access http://localhost:3000/a to get a 404 error and open the console. I can type anything but nothing happens when I press the return key. It’s completely ignored and the cursor keeps staying on the same line. I tested that with Firefox 34.0 and Opera 26.0 on Ubuntu 12.04.5, Ruby 2.1.0 and Ruby 2.2.0. Another possibly related strange behaviour is that no console appears if I add console into a controller (rails g controller welcome, action index) or <%= console %> in a view (welcome/index.html.erb).