diff --git a/WebRoot/include/mutifile/package.json b/WebRoot/include/mutifile/package.json
index a25905a..8929fd3 100644
--- a/WebRoot/include/mutifile/package.json
+++ b/WebRoot/include/mutifile/package.json
@@ -36,7 +36,7 @@
     "grunt-contrib-uglify": "^0.4.0",
     "selenium-webdriver": "^2.41.0",
     "grunt-contrib-cssmin": "^0.9.0",
-    "clean-css": "^2.1.8",
+    "clean-css": "^4.2.1",
     "html-minifier": "^0.5.6",
     "grunt-contrib-jade": "^0.11.0",
     "grunt-shell": "^0.6.4",