diff --git a/src/shared/utils/base/ui.js b/src/shared/utils/base/ui.js
index 9bac63f4..c5b2ab4f 100644
--- a/src/shared/utils/base/ui.js
+++ b/src/shared/utils/base/ui.js
@@ -75,8 +75,7 @@ function changeAppThemeStyle(themeMode) {
     let themeConfig = THEME_CONFIG[themeMode];
     if (!themeConfig) {
         console.error('Invalid theme mode:', themeMode);
-        // load system theme as fallback
-        themeMode = systemIsDarkMode() ? 'dark' : 'light';
+        themeMode = 'dark';
         themeConfig = THEME_CONFIG[themeMode];
         const appSettingsStore = useAppearanceSettingsStore();
         appSettingsStore.setThemeMode(themeMode);
diff --git a/src/stores/settings/appearance.js b/src/stores/settings/appearance.js
index 152e985f..066b12ec 100644
--- a/src/stores/settings/appearance.js
+++ b/src/stores/settings/appearance.js
@@ -286,9 +286,11 @@ export const useAppearanceSettingsStore = defineStore(
         );
 
         function normalizeThemeMode(mode) {
-            return Object.prototype.hasOwnProperty.call(THEME_CONFIG, mode)
-                ? mode
-                : 'light';
+            if (Object.prototype.hasOwnProperty.call(THEME_CONFIG, mode)) {
+                return mode;
+            } else {
+                return 'dark';
+            }
         }
 
         /**