diff --git a/build.sbt b/build.sbt
index 89b4c31..f3dddf6 100755
--- a/build.sbt
+++ b/build.sbt
@@ -19,7 +19,7 @@ addSbtWeb("1.5.3")
 libraryDependencies ++= Seq(
   "org.webjars" % "less-node" % "2.7.2-1",
   "org.webjars" % "mkdirp" % "0.5.0",
-  "org.webjars.npm" % "clean-css" % "4.0.5",
+  "org.webjars.npm" % "clean-css" % "4.2.4",
   "org.webjars.npm" % "less-plugin-clean-css" % "1.5.1" intransitive(),
   "org.webjars" % "es6-promise-node" % "2.1.1"
 )