diff --git a/src/node/markdown/plugins/highlight.ts b/src/node/markdown/plugins/highlight.ts
index 8e34e813ee57..0b373475a9be 100644
--- a/src/node/markdown/plugins/highlight.ts
+++ b/src/node/markdown/plugins/highlight.ts
@@ -14,7 +14,7 @@ export async function highlight(theme: ThemeOptions = 'material-palenight') {
 
   return (str: string, lang: string) => {
     const vPre = vueRE.test(lang) ? '' : 'v-pre'
-    lang = lang.replace(vueRE, '')
+    lang = lang.replace(vueRE, '').toLowerCase()
 
     if (hasSingleTheme) {
       return highlighter