diff --git a/library/Icinga/Authentication/Auth.php b/library/Icinga/Authentication/Auth.php
index fa5b52868..d56d3789b 100644
--- a/library/Icinga/Authentication/Auth.php
+++ b/library/Icinga/Authentication/Auth.php
@@ -104,14 +104,19 @@ class Auth
         // Reload CSS if the theme changed
         $themingConfig = Icinga::app()->getConfig()->getSection('themes');
         $userTheme = $user->getPreferences()->getValue('icingaweb', 'theme');
-        $themeMode = $user->getPreferences()->getValue('icingaweb', 'theme_mode');
         if (! (bool) $themingConfig->get('disabled', false) && $userTheme !== null) {
             $defaultTheme = $themingConfig->get('default', StyleSheet::DEFAULT_THEME);
-            if (($userTheme !== $defaultTheme) || ($themeMode !== StyleSheet::DEFAULT_MODE)) {
+            if ($userTheme !== $defaultTheme) {
                 $this->getResponse()->setReloadCss(true);
             }
         }
 
+        // Also reload CSS if the theme mode changed
+        $themeMode = $user->getPreferences()->getValue('icingaweb', 'theme_mode');
+        if ($themeMode && $themeMode !== StyleSheet::DEFAULT_MODE) {
+            $this->getResponse()->setReloadCss(true);
+        }
+
         // Reload entire layout if the locale changed
         if (($locale = $user->getPreferences()->getValue('icingaweb', 'language')) !== null) {
             if (setlocale(LC_ALL, 0) !== $locale && $this->getRequest()->isXmlHttpRequest()) {