diff --git a/lib/build/webpack/client.config.js b/lib/build/webpack/client.config.js
index b471b9e6d1..0a8e1a1975 100644
--- a/lib/build/webpack/client.config.js
+++ b/lib/build/webpack/client.config.js
@@ -72,5 +72,12 @@ module.exports = function () {
       })
     )
   }
+  // Extend config
+  if (typeof this.options.build.extend === 'function') {
+    this.options.build.extend(config, {
+      dev: this.dev,
+      isClient: true
+    })
+  }
   return config
 }
diff --git a/lib/build/webpack/server.config.js b/lib/build/webpack/server.config.js
index 5371f40962..09dbc80708 100644
--- a/lib/build/webpack/server.config.js
+++ b/lib/build/webpack/server.config.js
@@ -51,6 +51,12 @@ module.exports = function () {
   }
   config.externals = uniq(config.externals)
 
-  // Return config
+  // Extend config
+  if (typeof this.options.build.extend === 'function') {
+    this.options.build.extend(config, {
+      dev: this.dev,
+      isServer: true
+    })
+  }
   return config
 }