diff --git a/lib/build.js b/lib/build.js
index 307a06a4..5fe33cc2 100644
--- a/lib/build.js
+++ b/lib/build.js
@@ -70,6 +70,6 @@ exports.run = function(dir, additionalConfig) {
 };
 
 exports.watch = function(dir, additionalConfig, cb) {
-  var compiler = webpack(webpackConfig(dir));
-  compiler.watch(webpackConfig(dir), cb);
+  var compiler = webpack(webpackConfig(dir, additionalConfig));
+  compiler.watch(webpackConfig(dir, additionalConfig), cb);
 };