diff --git a/amp-article/package-lock.json b/amp-article/package-lock.json
index a97841afe..991ee9315 100644
--- a/amp-article/package-lock.json
+++ b/amp-article/package-lock.json
@@ -1670,9 +1670,9 @@
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     },
     "clean-css": {
-      "version": "4.2.1",
-      "resolved": "https://registry.npmjs.org/clean-css/-/clean-css-4.2.1.tgz",
-      "integrity": "sha512-4ZxI6dy4lrY6FHzfiy1aEOXgu4LIsW2MhwG0VBKdcoGoH/XLFgaHSdLTGr4O8Be6A8r3MOphEiI8Gc1n0ecf3g==",
+      "version": "4.2.4",
+      "resolved": "https://registry.npmjs.org/clean-css/-/clean-css-4.2.4.tgz",
+      "integrity": "sha512-EJUDT7nDVFDvaQgAo2G/PJvxmp1o/c6iXLbswsBbUFXi1Nr+AjA2cKmfbKDMjMvzEe75g3P6JkaDDAKk96A85A==",
       "requires": {
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       },
diff --git a/amp-article/package.json b/amp-article/package.json
index cd7e2b89e..440a6a300 100644
--- a/amp-article/package.json
+++ b/amp-article/package.json
@@ -14,7 +14,7 @@
   },
   "dependencies": {
     "@babel/preset-react": "7.0.0",
-    "clean-css": "4.2.1",
+    "clean-css": "4.2.4",
     "midori": "3.3.0",
     "node-fetch": "2.3.0",
     "ramda": "0.26.1",
diff --git a/amp-stories/package-lock.json b/amp-stories/package-lock.json
index a7b3c3840..16b4a113e 100644
--- a/amp-stories/package-lock.json
+++ b/amp-stories/package-lock.json
@@ -1661,9 +1661,9 @@
       }
     },
     "clean-css": {
-      "version": "4.2.1",
-      "resolved": "https://registry.npmjs.org/clean-css/-/clean-css-4.2.1.tgz",
-      "integrity": "sha512-4ZxI6dy4lrY6FHzfiy1aEOXgu4LIsW2MhwG0VBKdcoGoH/XLFgaHSdLTGr4O8Be6A8r3MOphEiI8Gc1n0ecf3g==",
+      "version": "4.2.4",
+      "resolved": "https://registry.npmjs.org/clean-css/-/clean-css-4.2.4.tgz",
+      "integrity": "sha512-EJUDT7nDVFDvaQgAo2G/PJvxmp1o/c6iXLbswsBbUFXi1Nr+AjA2cKmfbKDMjMvzEe75g3P6JkaDDAKk96A85A==",
       "requires": {
         "source-map": "~0.6.0"
       },
diff --git a/amp-stories/package.json b/amp-stories/package.json
index b3618b74e..036fcd727 100644
--- a/amp-stories/package.json
+++ b/amp-stories/package.json
@@ -19,7 +19,7 @@
   "dependencies": {
     "@babel/preset-react": "7.0.0",
     "babel-plugin-styled-components": "^1.10.6",
-    "clean-css": "4.2.1",
+    "clean-css": "4.2.4",
     "http-server": "^0.11.1",
     "js-beautify": "^1.10.2",
     "midori": "3.3.0",