diff --git a/web_src/js/features/codemirror-lang.ts b/web_src/js/features/codemirror-lang.ts
index 729f617a3e..27b4d20a1d 100644
--- a/web_src/js/features/codemirror-lang.ts
+++ b/web_src/js/features/codemirror-lang.ts
@@ -9,6 +9,13 @@ export function languages(codemirrorLanguage: CodeMirrorLanguage): LanguageDescr
         return (await import('@codemirror/lang-cpp')).cpp();
       },
     }),
+    codemirrorLanguage.LanguageDescription.of({
+      name: 'C3',
+      extensions: ['c3'],
+      async load() {
+        return (await import('@codemirror/lang-cpp')).cpp();
+      },
+    }),
     codemirrorLanguage.LanguageDescription.of({
       name: 'C++',
       alias: ['cpp'],