diff --git a/src/theme/ThemeRegistry.tsx b/src/theme/ThemeRegistry.tsx
index e2628bf..22c9831 100644
--- a/src/theme/ThemeRegistry.tsx
+++ b/src/theme/ThemeRegistry.tsx
@@ -17,7 +17,7 @@ const getLocalizationFromLang = (lang: string) => {
 // Copied from https://github.com/mui/material-ui/blob/master/examples/material-ui-nextjs-ts/src/components/ThemeRegistry/ThemeRegistry.tsx
 export default function ThemeRegistry({
   children,
-  lang,
+  lang = "zh",
 }: {
   children: React.ReactNode;
   lang: string;
@@ -28,7 +28,7 @@ export default function ThemeRegistry({
   );
   return (
     <NextAppDirEmotionCacheProvider options={{ key: "mui" }}>
-      <ThemeProvider theme={theme}>
+      <ThemeProvider theme={themeWithLocale}>
         <CssBaseline />
         {children}
       </ThemeProvider>