Using Devise in a Mountable Engine Rails from outside of the engine -

i have engine called hq_core, , have rails app called hq.

hq_core has devise user installed within , works hq. did using this how-to

i want create devise admin_user in hq, not hq_core. ran typical 'rails g devise admin_user' installed find in hq.

but when hit localhost:3000/admin_users/sign_in, says

actionview::template::error (undefined method `admin_user_session_path' #<actiondispatch::routing::routesproxy:0x007fb454403818>): 

this rails 4 application devise 3.0.0rc

i had same problem solved adding

devise.setup |config|   config.router_name = :<your engine name here> end 

to config/initializers/devise.rb stated in how to.