diff --git a/src/transforms/posthtml.js b/src/transforms/posthtml.js
index 5fa3e377a02..c9f8ebaaa58 100644
--- a/src/transforms/posthtml.js
+++ b/src/transforms/posthtml.js
@@ -33,7 +33,10 @@ async function getConfig(asset) {
   if (asset.options.minify) {
     const htmlNanoConfig = asset.package.htmlnano ||
       (await asset.getConfig(['.htmlnanorc', '.htmlnanorc.js'])) || {
-        collapseWhitespace: 'conservative'
+        collapseWhitespace: 'conservative',
+        minifyCss: {
+          safe: true
+        }
       };
 
     config.plugins.push(htmlnano(htmlNanoConfig));
diff --git a/yarn.lock b/yarn.lock
index 9ddae5ec46f..f62d3b86bcb 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3248,7 +3248,7 @@ lcid@^1.0.0:
   dependencies:
     invert-kv "^1.0.0"
 
-less@^3.0.0:
+less@^3.0.1:
   version "3.0.1"
   resolved "https://registry.yarnpkg.com/less/-/less-3.0.1.tgz#ba2fea24a5632ccb8c84230d6043c0bf91855e37"
   optionalDependencies: