diff --git a/init.rb b/init.rb
index 91f56d5..87cbaf3 100644
--- a/init.rb
+++ b/init.rb
@@ -4,7 +4,11 @@
 # Patches to the Redmine core.
 require 'dispatcher' unless Rails::VERSION::MAJOR >= 3
 
-if Rails::VERSION::MAJOR >= 3
+if Rails::VERSION::MAJOR >= 5
+  ActiveSupport::Reloader.to_prepare do
+    require_dependency 'redmine_incoming_emails/patches/mail_handler_patch'
+  end
+elsif Rails::VERSION::MAJOR >= 3
   ActionDispatch::Callbacks.to_prepare do
     require_dependency 'redmine_incoming_emails/patches/mail_handler_patch'
   end
diff --git a/lib/redmine_incoming_emails/patches/mail_handler_patch.rb b/lib/redmine_incoming_emails/patches/mail_handler_patch.rb
index 9ffe80b..b7347b2 100644
--- a/lib/redmine_incoming_emails/patches/mail_handler_patch.rb
+++ b/lib/redmine_incoming_emails/patches/mail_handler_patch.rb
@@ -11,7 +11,8 @@ def self.included(base) # :nodoc:
         base.class_eval do
           unloadable
           
-          alias_method_chain :target_project, :user_specific_defaults
+          alias_method :target_project_without_user_specific_defaults, :target_project
+          alias_method :target_project, :target_project_with_user_specific_defaults
         end
       end