diff --git a/lib/plugins/acts_as_attachable/lib/acts_as_attachable.rb b/lib/plugins/acts_as_attachable/lib/acts_as_attachable.rb
index e86b83e..ff1ee23 100644
--- a/lib/plugins/acts_as_attachable/lib/acts_as_attachable.rb
+++ b/lib/plugins/acts_as_attachable/lib/acts_as_attachable.rb
@@ -31,7 +31,7 @@ module Redmine
           attachable_options[:delete_permission] = options.delete(:delete_permission) || "edit_#{self.name.pluralize.underscore}".to_sym
 
           has_many :attachments, lambda {order("#{Attachment.table_name}.created_on ASC, #{Attachment.table_name}.id ASC")},
-                                 options.merge(:as => :container, :dependent => :destroy)
+                                 options.merge(:as => :container, :dependent => :destroy, :inverse_of => :container)
           send :include, Redmine::Acts::Attachable::InstanceMethods
           before_save :attach_saved_attachments
         end