diff --git a/application/forms/PreferenceForm.php b/application/forms/PreferenceForm.php
index 6ab2ade3a..df6733b34 100644
--- a/application/forms/PreferenceForm.php
+++ b/application/forms/PreferenceForm.php
@@ -186,6 +186,7 @@ class PreferenceForm extends Form
             );
         }
 
+        $themeFile = StyleSheet::getThemeFile(Config::app()->get('themes', 'default'));
         if (! (bool) Config::app()->get('themes', 'disabled', false)) {
             $themes = Icinga::app()->getThemes();
             if (count($themes) > 1) {
@@ -212,7 +213,10 @@ class PreferenceForm extends Form
 
         if (isset($formData['theme']) && $formData['theme'] !== StyleSheet::DEFAULT_THEME) {
             $themeFile = StyleSheet::getThemeFile($formData['theme']);
-            $file = $themeFile !== null ? @file_get_contents($themeFile) : false;
+        }
+
+        if ($themeFile !== null) {
+            $file = @file_get_contents($themeFile);
             if ($file && strpos($file, StyleSheet::LIGHT_MODE_IDENTIFIER) === false) {
                 $disabled = ['', 'light', 'system'];
             }