diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 205817e44c..1dee3f96a8 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -165,6 +165,7 @@ module ApplicationHelper
       class: html_classes,
       'data-contrast': contrast.parameterize,
       'data-color-scheme': page_color_scheme.parameterize,
+      'data-user-flavour': current_flavour.parameterize,
     }
 
     base[:'data-system-theme'] = 'true' if page_color_scheme == 'auto'
diff --git a/app/views/layouts/embedded.html.haml b/app/views/layouts/embedded.html.haml
index b7422bebcf..d4697a4af5 100644
--- a/app/views/layouts/embedded.html.haml
+++ b/app/views/layouts/embedded.html.haml
@@ -1,5 +1,5 @@
 !!! 5
-%html{ lang: I18n.locale, 'data-contrast': 'auto', 'data-color-scheme': 'light' }
+%html{ lang: I18n.locale, 'data-contrast': 'auto', 'data-color-scheme': 'light', 'data-user-flavour': current_flavour.parameterize }
   %head
     %meta{ charset: 'utf-8' }/
     %meta{ name: 'robots', content: 'noindex' }/
diff --git a/app/views/layouts/error.html.haml b/app/views/layouts/error.html.haml
index c696eea57d..463fccfd47 100644
--- a/app/views/layouts/error.html.haml
+++ b/app/views/layouts/error.html.haml
@@ -1,5 +1,5 @@
 !!!
-%html{ lang: I18n.locale, 'data-contrast': 'auto', 'data-color-scheme': 'auto' }
+%html{ lang: I18n.locale, 'data-contrast': 'auto', 'data-color-scheme': 'auto', 'data-user-flavour': current_flavour.parameterize }
   %head
     %meta{ 'content' => 'text/html; charset=UTF-8', 'http-equiv' => 'Content-Type' }/
     %meta{ charset: 'utf-8' }/