diff --git a/package.json b/package.json
index 3b23931..00711aa 100644
--- a/package.json
+++ b/package.json
@@ -25,7 +25,7 @@
   "dependencies": {
     "cheerio": "1.0.0-rc.3",
     "css-tree": "1.0.0-alpha.39",
-    "csso": "4.0.3",
+    "csso": "4.1.0",
     "filesize": "^6.0.0",
     "minimist": "^1.2.0",
     "puppeteer": "^2.0.0"
diff --git a/yarn.lock b/yarn.lock
index 5c28dd8..212b22e 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1230,17 +1230,25 @@ css-tree@1.0.0-alpha.39:
     mdn-data "2.0.6"
     source-map "^0.6.1"
 
+css-tree@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/css-tree/-/css-tree-1.0.0.tgz#21993fa270d742642a90409a2c0cb3ac0298adf6"
+  integrity sha512-CdVYz/Yuqw0VdKhXPBIgi8DO3NicJVYZNWeX9XcIuSp9ZoFT5IcleVRW07O5rMjdcx1mb+MEJPknTTEW7DdsYw==
+  dependencies:
+    mdn-data "2.0.12"
+    source-map "^0.6.1"
+
 css-what@2.1:
   version "2.1.3"
   resolved "https://registry.yarnpkg.com/css-what/-/css-what-2.1.3.tgz#a6d7604573365fe74686c3f311c56513d88285f2"
   integrity sha512-a+EPoD+uZiNfh+5fxw2nO9QwFa6nJe2Or35fGY6Ipw1R3R4AGz1d1TEZrCegvw2YTmZ0jXirGYlzxxpYSHwpEg==
 
-csso@4.0.3:
-  version "4.0.3"
-  resolved "https://registry.yarnpkg.com/csso/-/csso-4.0.3.tgz#0d9985dc852c7cc2b2cacfbbe1079014d1a8e903"
-  integrity sha512-NL3spysxUkcrOgnpsT4Xdl2aiEiBG6bXswAABQVHcMrfjjBisFOKwLDOmf4wf32aPdcJws1zds2B0Rg+jqMyHQ==
+csso@4.1.0:
+  version "4.1.0"
+  resolved "https://registry.yarnpkg.com/csso/-/csso-4.1.0.tgz#1d31193efa99b87aa6bad6c0cef155e543d09e8b"
+  integrity sha512-h+6w/W1WqXaJA4tb1dk7r5tVbOm97MsKxzwnvOR04UQ6GILroryjMWu3pmCCtL2mLaEStQ0fZgeGiy99mo7iyg==
   dependencies:
-    css-tree "1.0.0-alpha.39"
+    css-tree "^1.0.0"
 
 cssom@^0.4.4:
   version "0.4.4"
@@ -2838,6 +2846,11 @@ map-visit@^1.0.0:
   dependencies:
     object-visit "^1.0.0"
 
+mdn-data@2.0.12:
+  version "2.0.12"
+  resolved "https://registry.yarnpkg.com/mdn-data/-/mdn-data-2.0.12.tgz#bbb658d08b38f574bbb88f7b83703defdcc46844"
+  integrity sha512-ULbAlgzVb8IqZ0Hsxm6hHSlQl3Jckst2YEQS7fODu9ilNWy2LvcoSY7TRFIktABP2mdppBioc66va90T+NUs8Q==
+
 mdn-data@2.0.6:
   version "2.0.6"
   resolved "https://registry.yarnpkg.com/mdn-data/-/mdn-data-2.0.6.tgz#852dc60fcaa5daa2e8cf6c9189c440ed3e042978"