diff --git a/core/templates/layout.guest.php b/core/templates/layout.guest.php
index 64bec6de9be..0723e90173b 100644
--- a/core/templates/layout.guest.php
+++ b/core/templates/layout.guest.php
@@ -35,7 +35,9 @@ p($theme->getTitle());
 		<?php emit_script_loading_tags($_); ?>
 		<?php print_unescaped($_['headers']); ?>
 	</head>
-	<body id="<?php p($_['bodyid']);?>">
+	<body id="<?php p($_['bodyid']);?>" <?php foreach ($_['enabledThemes'] as $themeId) {
+		p("data-theme-$themeId ");
+	}?> data-themes="<?php p(join(',', $_['enabledThemes'])) ?>">
 		<?php include 'layout.noscript.warning.php'; ?>
 		<?php include 'layout.initial-state.php'; ?>
 		<div class="wrapper">
diff --git a/lib/private/TemplateLayout.php b/lib/private/TemplateLayout.php
index 01d22edc0fb..ae7b1f47dca 100644
--- a/lib/private/TemplateLayout.php
+++ b/lib/private/TemplateLayout.php
@@ -149,6 +149,13 @@ class TemplateLayout {
 				if ($user) {
 					$userDisplayName = $user->getDisplayName();
 				}
+
+				$page->assign('enabledThemes', []);
+				if ($this->appManager->isEnabledForUser('theming') && class_exists('\OCA\Theming\Service\ThemesService')) {
+					$themesService = Server::get(\OCA\Theming\Service\ThemesService::class);
+					$page->assign('enabledThemes', $themesService->getEnabledThemes());
+				}
+
 				$page->assign('user_displayname', $userDisplayName);
 				$page->assign('user_uid', \OC_User::getUser());
 				break;
