diff --git a/package.json b/package.json
index 815c9386..6ebf39e3 100644
--- a/package.json
+++ b/package.json
@@ -34,7 +34,7 @@
     "@11ty/eleventy-plugin-rss": "^1.1.1",
     "@tryghost/content-api": "^1.4.4",
     "@tryghost/helpers": "^1.1.6",
-    "clean-css": "^4.2.1",
+    "clean-css": "^5.0.0",
     "cross-env": "^7.0.0",
     "dotenv": "^8.0.0",
     "eleventy-plugin-lazyimages": "liamfiddler/eleventy-plugin-lazyimages",
diff --git a/yarn.lock b/yarn.lock
index cb4c5186..5252acd1 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1026,6 +1026,13 @@ clean-css@^4.1.11, clean-css@^4.2.1:
   dependencies:
     source-map "~0.6.0"
 
+clean-css@^5.0.0:
+  version "5.1.3"
+  resolved "https://registry.yarnpkg.com/clean-css/-/clean-css-5.1.3.tgz#42348778c3acb0083946ba340896802be5517ee2"
+  integrity sha512-qGXzUCDpLwAlPx0kYeU4QXjzQIcIYZbJjD4FNm7NnSjoP0hYMVZhHOpUYJ6AwfkMX2cceLRq54MeCgHy/va1cA==
+  dependencies:
+    source-map "~0.6.0"
+
 clean-regexp@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/clean-regexp/-/clean-regexp-1.0.0.tgz#8df7c7aae51fd36874e8f8d05b9180bc11a3fed7"