diff --git a/lib/email_prefixer/railtie.rb b/lib/email_prefixer/railtie.rb
index b4fc0bb..5e5ce5c 100644
--- a/lib/email_prefixer/railtie.rb
+++ b/lib/email_prefixer/railtie.rb
@@ -2,7 +2,11 @@ module EmailPrefixer
   class Railtie < ::Rails::Railtie
     initializer 'email_prefixer.configure_defaults' do |app|
       config = EmailPrefixer.configure do |config|
-        config.application_name ||= app.class.parent_name
+        config.application_name ||= if app.class.respond_to?(:module_parent_name)
+            app.class.module_parent_name
+          else
+            app.class.parent_name
+          end
         config.stage_name ||= Rails.env
         config.builder ||= EmailPrefixer::Configuration::DEFAULT_BUILDER
       end