diff --git a/app/mailers/user_notifications.rb b/app/mailers/user_notifications.rb
index c7c3832e4c2..4b9ffa27253 100644
--- a/app/mailers/user_notifications.rb
+++ b/app/mailers/user_notifications.rb
@@ -333,7 +333,7 @@ class UserNotifications < ActionMailer::Base
         invite_template = "user_notifications.invited_to_topic_body"
       end
       topic_excerpt = post.excerpt.gsub("\n", " ") if post.is_first_post? && post.excerpt
-      message = I18n.t(invite_template, username: post.username, topic_title: title, topic_excerpt: topic_excerpt, site_title: SiteSetting.title, site_description: SiteSetting.site_description)
+      message = I18n.t(invite_template, username: username, topic_title: title, topic_excerpt: topic_excerpt, site_title: SiteSetting.title, site_description: SiteSetting.site_description)
       html = UserNotificationRenderer.new(Rails.configuration.paths["app/views"]).render(
         template: 'email/invite',
         format: :html,