diff --git a/package.json b/package.json
index bbd8cec..1e3c608 100644
--- a/package.json
+++ b/package.json
@@ -16,8 +16,8 @@
     "url": "https://github.com/nokonoko/uguu/issues"
   },
   "devDependencies": {
-    "clean-css": "^4.2.1",
-    "clean-css-cli": "^4.3.0",
+    "clean-css": "^5.1.2",
+    "clean-css-cli": "^5.3.0",
     "uglify-js": "^3.13.9",
     "swig": "^1.4.2"
   },