diff --git a/package-lock.json b/package-lock.json
index 9848576..fe867e3 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -29,7 +29,8 @@
     "amdefine": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/amdefine/-/amdefine-1.0.0.tgz",
-      "integrity": "sha1-/RdHRwDLXMnCtwnwvp0jzjwZjDM="
+      "integrity": "sha1-/RdHRwDLXMnCtwnwvp0jzjwZjDM=",
+      "dev": true
     },
     "asap": {
       "version": "1.0.0",
@@ -54,30 +55,11 @@
       "dev": true
     },
     "clean-css": {
-      "version": "3.4.22",
-      "resolved": "https://registry.npmjs.org/clean-css/-/clean-css-3.4.22.tgz",
-      "integrity": "sha1-2zIwZPdSAod4IztYxUzYU1+GCJI=",
+      "version": "4.1.11",
+      "resolved": "https://registry.npmjs.org/clean-css/-/clean-css-4.1.11.tgz",
+      "integrity": "sha1-Ls3xRaujj1R0DybO/Q/z4D4SXWo=",
       "requires": {
-        "commander": "2.8.1",
-        "source-map": "0.4.4"
-      },
-      "dependencies": {
-        "commander": {
-          "version": "2.8.1",
-          "resolved": "https://registry.npmjs.org/commander/-/commander-2.8.1.tgz",
-          "integrity": "sha1-Br42f+v9oMMwqh4qBy09yXYkJdQ=",
-          "requires": {
-            "graceful-readlink": "1.0.1"
-          }
-        },
-        "source-map": {
-          "version": "0.4.4",
-          "resolved": "https://registry.npmjs.org/source-map/-/source-map-0.4.4.tgz",
-          "integrity": "sha1-66T12pwNyZneaAMti092FzZSA2s=",
-          "requires": {
-            "amdefine": "1.0.0"
-          }
-        }
+        "source-map": "0.5.x"
       }
     },
     "commander": {
@@ -221,7 +203,8 @@
     "graceful-readlink": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/graceful-readlink/-/graceful-readlink-1.0.1.tgz",
-      "integrity": "sha1-TK+tdrxi8C+gObL5Tpo906ORpyU="
+      "integrity": "sha1-TK+tdrxi8C+gObL5Tpo906ORpyU=",
+      "dev": true
     },
     "grunt": {
       "version": "0.4.5",
@@ -1009,6 +992,27 @@
               "integrity": "sha1-wN3kqxgnE7kZuXCVmhI+zBow/NY=",
               "dev": true
             },
+            "clean-css": {
+              "version": "3.4.22",
+              "resolved": "https://registry.npmjs.org/clean-css/-/clean-css-3.4.22.tgz",
+              "integrity": "sha1-2zIwZPdSAod4IztYxUzYU1+GCJI=",
+              "dev": true,
+              "requires": {
+                "commander": "2.8.x",
+                "source-map": "0.4.x"
+              },
+              "dependencies": {
+                "commander": {
+                  "version": "2.8.1",
+                  "resolved": "https://registry.npmjs.org/commander/-/commander-2.8.1.tgz",
+                  "integrity": "sha1-Br42f+v9oMMwqh4qBy09yXYkJdQ=",
+                  "dev": true,
+                  "requires": {
+                    "graceful-readlink": ">= 1.0.0"
+                  }
+                }
+              }
+            },
             "commander": {
               "version": "2.6.0",
               "resolved": "https://registry.npmjs.org/commander/-/commander-2.6.0.tgz",
@@ -1179,6 +1183,7 @@
           "version": "0.4.4",
           "resolved": "https://registry.npmjs.org/source-map/-/source-map-0.4.4.tgz",
           "integrity": "sha1-66T12pwNyZneaAMti092FzZSA2s=",
+          "dev": true,
           "requires": {
             "amdefine": "1.0.0"
           }
@@ -1206,6 +1211,11 @@
       "resolved": "https://registry.npmjs.org/longest/-/longest-1.0.1.tgz",
       "integrity": "sha1-MKCy2jj3N3DoKUoNIuZiXtd9AJc="
     },
+    "source-map": {
+      "version": "0.5.7",
+      "resolved": "https://registry.npmjs.org/source-map/-/source-map-0.5.7.tgz",
+      "integrity": "sha1-igOdLRAh0i0eoUyA2OpGi6LvP8w="
+    },
     "uglify-js": {
       "version": "2.7.5",
       "resolved": "https://registry.npmjs.org/uglify-js/-/uglify-js-2.7.5.tgz",
diff --git a/package.json b/package.json
index ba438fa..c07840e 100644
--- a/package.json
+++ b/package.json
@@ -32,7 +32,7 @@
   },
   "dependencies": {
     "acorn": "^4.0.3",
-    "clean-css": "^3.4.22",
+    "clean-css": "^4.1.11",
     "uglify-js": "^2.7.5",
     "with": "^5.1.1"
   }