diff --git a/packages/@vuepress/types/index.js b/packages/@vuepress/types/index.js
index 37cf6d9cd6..5db556f90e 100644
--- a/packages/@vuepress/types/index.js
+++ b/packages/@vuepress/types/index.js
@@ -1,5 +1,5 @@
 function define(config) {
-  config;
+  return config;
 }
 exports.defineConfig = define;
 exports.defineConfig4CustomTheme = define;