diff --git a/package.json b/package.json
index 946c3540c0..f6f27b610c 100644
--- a/package.json
+++ b/package.json
@@ -19,7 +19,7 @@
     "build": "npm run build-cjs && npm run build-es6",
     "build-cjs": "rimraf lib && babel ./modules -d lib --ignore '__tests__'",
     "build-es6": "rimraf es6 && babel ./modules -d es6 --blacklist=es6.modules --ignore '__tests__'",
-    "build-umd": "NODE_ENV=production webpack modules/index.js umd/ReactRouter.js",
+    "build-umd": "NODE_ENV=development webpack modules/index.js umd/ReactRouter.js",
     "build-min": "NODE_ENV=production webpack -p modules/index.js umd/ReactRouter.min.js",
     "lint": "eslint modules examples",
     "start": "node examples/server.js",