diff --git a/README.md b/README.md
index 77e504650..f17687b97 100644
--- a/README.md
+++ b/README.md
@@ -76,7 +76,7 @@ Day.js has great support for internationalization.
 But none of them will be included in your build unless you use it.
 
 ```javascript
-import 'dayjs/locale/es' // load on demand
+import 'dayjs/locale/es.js' // load on demand
 
 dayjs.locale('es') // use Spanish locale globally
 
@@ -90,7 +90,7 @@ dayjs('2018-05-05').locale('zh-cn').format() // use Chinese Simplified locale in
 A plugin is an independent module that can be added to Day.js to extend functionality or add new features.
 
 ```javascript
-import advancedFormat from 'dayjs/plugin/advancedFormat' // load on demand
+import advancedFormat from 'dayjs/plugin/advancedFormat.js' // load on demand
 
 dayjs.extend(advancedFormat) // use plugin
 
diff --git a/babel.config.js b/babel.config.js
index 2531938f6..778b8a811 100644
--- a/babel.config.js
+++ b/babel.config.js
@@ -14,6 +14,9 @@ module.exports = {
             loose: true
           }
         ]
+      ],
+      plugins: [
+        ['add-import-extension', { extension: 'js' }]
       ]
     }
   }
diff --git a/package.json b/package.json
index e2baf268a..4e54b1b7c 100644
--- a/package.json
+++ b/package.json
@@ -58,6 +58,7 @@
     "@semantic-release/github": "^11.0.4",
     "babel-core": "^7.0.0-bridge.0",
     "babel-jest": "^22.4.3",
+    "babel-plugin-add-import-extension": "^1.6.0",
     "babel-plugin-external-helpers": "^6.22.0",
     "cross-env": "^5.1.6",
     "eslint": "^4.19.1",