diff --git a/package.json b/package.json
index d526162..68c8b53 100644
--- a/package.json
+++ b/package.json
@@ -26,7 +26,7 @@
     "animate.css": "^3.5.2"
   },
   "devDependencies": {
-    "clean-css": "^3.4.20",
+    "clean-css": "^4.2.3",
     "connect": "^3.5.0",
     "serve-static": "^1.11.1",
     "stylus": "^0.54.5"