diff --git a/tsup.config.ts b/tsup.config.ts
index d2d215c..ffeed64 100644
--- a/tsup.config.ts
+++ b/tsup.config.ts
@@ -7,4 +7,5 @@ export default createLibraryConfig({
     'phonetic/index': 'src/phonetic/index.ts',
     'data-structures/index': 'src/data-structures/index.ts',
   },
+  format: ['esm', 'cjs'],
 });