rails g administrate:install error

Created by: tengju

Hi its my first time trying to use this gem but when i genereate it this error keeps popping up.

/gems/ruby-2.3.1@global/gems/railties-4.2.6/lib/rails/generators/named_base.rb:102:in block in class_name': undefined methodcamelize' for nil:NilClass (NoMethodError)

How can i fix this? or what is exactly the problem?

p.s im using rails 4.2.6 with ruby 2.3.1