diff --git a/packages/runtime/src/Plugin/Plugin.ts b/packages/runtime/src/Plugin/Plugin.ts
index a2d6db66ba7f..40fc7911cd33 100644
--- a/packages/runtime/src/Plugin/Plugin.ts
+++ b/packages/runtime/src/Plugin/Plugin.ts
@@ -41,6 +41,8 @@ export default class Plugin {
     assert(!!plugin.apply, `register failed, plugin.apply must supplied`);
     assert(!!plugin.path, `register failed, plugin.path must supplied`);
     Object.keys(plugin.apply).forEach((key) => {
+      // workaround for https://github.com/umijs/mako/issues/1657
+      // root cause: mako bundler will add a default export to an empty module
       if (key === 'default') {
         return;
       }