diff --git a/static/src/bootstrap/package.json b/static/src/bootstrap/package.json
index 4773a3ff..a399d2ff 100644
--- a/static/src/bootstrap/package.json
+++ b/static/src/bootstrap/package.json
@@ -53,7 +53,7 @@
     "babel-eslint": "^7.1.1",
     "babel-plugin-transform-es2015-modules-strip": "^0.1.0",
     "babel-preset-es2015": "^6.18.0",
-    "clean-css": "^3.4.23",
+    "clean-css": "^4.2.1",
     "eslint": "^3.12.2",
     "grunt": "^1.0.1",
     "grunt-babel": "^6.0.0",