Redirect to sign in page after signup, this will show the correct flash message.

app/controllers/registrations_controller.rb

@@ -15,6 +15,14 @@ class RegistrationsController < Devise::RegistrationsController
     super
   end
 
+  def after_sign_up_path_for resource
+    new_user_session_path
+  end
+
+  def after_inactive_sign_up_path_for resource
+    new_user_session_path
+  end
+
   private
 
   def signup_enabled?