Accessing custom header variables in Ruby on Rails

Yes, it has changed in Rails 4. Take a look at the Http::Headers code.

Now custom variables are always prepended with HTTP_ and _ in your variables are replaced with -, except for CGI variables.

HTH

EDIT: Just checked again, - in variables are getting replaced with _ and being prepended with HTTP_. In above link, check line number 91-94:

key = key.upcase.tr('-', '_')