diff --git a/core/templates/layout.guest.php b/core/templates/layout.guest.php
index f006a6fda3818..a3c9d81082491 100644
--- a/core/templates/layout.guest.php
+++ b/core/templates/layout.guest.php
@@ -35,7 +35,9 @@
 		<?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(',', $_['enabledThemes'])) ?>">
 		<?php include 'layout.noscript.warning.php'; ?>
 		<?php include 'layout.initial-state.php'; ?>
 		<div class="wrapper">
diff --git a/lib/private/TemplateLayout.php b/lib/private/TemplateLayout.php
index 5ffcf8a03bb1f..86198a4d2c5c5 100644
--- a/lib/private/TemplateLayout.php
+++ b/lib/private/TemplateLayout.php
@@ -151,6 +151,8 @@ public function __construct($renderAs, $appId = '') {
 			if ($user) {
 				$userDisplayName = $user->getDisplayName();
 			}
+			$theme = $this->config->getSystemValueString('enforce_theme', '');
+			$this->assign('enabledThemes', $theme === '' ? [] : [$theme]);
 			$this->assign('user_displayname', $userDisplayName);
 			$this->assign('user_uid', \OC_User::getUser());
 		} elseif ($renderAs === TemplateResponse::RENDER_AS_PUBLIC) {
