diff --git a/package.json b/package.json
index aa4b1e0..fe3aba7 100644
--- a/package.json
+++ b/package.json
@@ -3,7 +3,7 @@
     "version": "1.0.0",
     "private": true,
     "devDependencies": {
-        "clean-css": "^3.4.12",
+        "clean-css": "^4.2.1",
         "csslint": "^0.10.0",
         "html-minifier": "^0.8.0",
         "htmlhint": "0.9.12",