diff --git a/platform/chromium/vapi-background.js b/platform/chromium/vapi-background.js
index 1ba429c94..b4d1fed01 100644
--- a/platform/chromium/vapi-background.js
+++ b/platform/chromium/vapi-background.js
@@ -39,10 +39,7 @@ vAPI.cantWebsocket =
 
 // https://issues.adblockplus.org/ticket/5695
 // - Good idea, adopted: cleaner way to detect user-stylesheet support.
-vAPI.supportsUserStylesheets = 
-    chrome.extensionTypes instanceof Object &&
-    chrome.extensionTypes.CSSOrigin instanceof Object &&
-    'USER' in chrome.extensionTypes.CSSOrigin;
+vAPI.supportsUserStylesheets = vAPI.webextFlavor.soup.has('user_stylesheet');
 vAPI.insertCSS = chrome.tabs.insertCSS;
 
 var noopFunc = function(){};
@@ -843,9 +840,11 @@ vAPI.messaging.onPortMessage = (function() {
                 details.code = cssText;
                 cssPromises.push(chrome.tabs.insertCSS(tabId, details));
             }
-            for ( cssText of msg.remove ) {
-                details.code = cssText;
-                cssPromises.push(chrome.tabs.removeCSS(tabId, details));
+            if ( typeof chrome.tabs.removeCSS === 'function' ) {
+                for ( cssText of msg.remove ) {
+                    details.code = cssText;
+                    cssPromises.push(chrome.tabs.removeCSS(tabId, details));
+                }
             }
             if ( typeof callback === 'function' ) {
                 Promise.all(cssPromises).then(() => {
diff --git a/platform/chromium/vapi-usercss.js b/platform/chromium/vapi-usercss.pseudo.js
similarity index 97%
rename from platform/chromium/vapi-usercss.js
rename to platform/chromium/vapi-usercss.pseudo.js
index df050cc97..142bab49e 100644
--- a/platform/chromium/vapi-usercss.js
+++ b/platform/chromium/vapi-usercss.pseudo.js
@@ -1,7 +1,7 @@
 /*******************************************************************************
 
     uBlock Origin - a browser extension to block requests.
-    Copyright (C) 2017 Raymond Hill
+    Copyright (C) 2017-2018 Raymond Hill
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -27,7 +27,15 @@
 //   https://github.com/chrisaljoudi/uBlock/issues/456
 //   https://github.com/gorhill/uBlock/issues/2029
 
-if ( typeof vAPI === 'object' ) { // >>>>>>>> start of HUGE-IF-BLOCK
+// https://github.com/gorhill/uBlock/issues/3588
+//   Chromium 66+ supports user stylesheets. Testing support against a regex is
+//   (unfortunately) necessary from content scripts.
+
+if (
+    typeof vAPI === 'object' &&
+    /\bEdge\/\d+|\bChrom(?:e|ium)\/(?:[45][0-9]|6[0-5])/.test(navigator.userAgent)
+) {
+// >>>>>>>> start of HUGE-IF-BLOCK
 
 /******************************************************************************/
 /******************************************************************************/
@@ -543,4 +551,5 @@ vAPI.DOMFilterer.prototype = {
 /******************************************************************************/
 /******************************************************************************/
 
-} // <<<<<<<< end of HUGE-IF-BLOCK
+// <<<<<<<< end of HUGE-IF-BLOCK
+}
diff --git a/platform/webext/vapi-usercss.js b/platform/chromium/vapi-usercss.real.js
similarity index 97%
rename from platform/webext/vapi-usercss.js
rename to platform/chromium/vapi-usercss.real.js
index 9db9bce1b..493a4b246 100644
--- a/platform/webext/vapi-usercss.js
+++ b/platform/chromium/vapi-usercss.real.js
@@ -1,7 +1,7 @@
 /*******************************************************************************
 
     uBlock Origin - a browser extension to block requests.
-    Copyright (C) 2017 Raymond Hill
+    Copyright (C) 2017-2018 Raymond Hill
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -23,7 +23,11 @@
 
 // For content pages
 
-if ( typeof vAPI === 'object' ) { // >>>>>>>> start of HUGE-IF-BLOCK
+if (
+    typeof vAPI === 'object' &&
+    vAPI.userStylesheet === undefined
+) {
+// >>>>>>>> start of HUGE-IF-BLOCK
 
 /******************************************************************************/
 /******************************************************************************/
@@ -237,4 +241,5 @@ vAPI.DOMFilterer.prototype = {
 /******************************************************************************/
 /******************************************************************************/
 
-} // <<<<<<<< end of HUGE-IF-BLOCK
+// <<<<<<<< end of HUGE-IF-BLOCK
+}
diff --git a/tools/make-chromium.sh b/tools/make-chromium.sh
index 2f3f06cab..dbec5535f 100755
--- a/tools/make-chromium.sh
+++ b/tools/make-chromium.sh
@@ -24,11 +24,14 @@ cp platform/chromium/*.json $DES/
 cp LICENSE.txt              $DES/
 
 echo "*** uBlock0.chromium: concatenating content scripts"
-cat $DES/js/vapi-usercss.js > /tmp/contentscript.js
+cat $DES/js/vapi-usercss.pseudo.js > /tmp/contentscript.js
+echo >> /tmp/contentscript.js
+grep -v "^'use strict';$" $DES/js/vapi-usercss.real.js >> /tmp/contentscript.js
 echo >> /tmp/contentscript.js
 grep -v "^'use strict';$" $DES/js/contentscript.js >> /tmp/contentscript.js
 mv /tmp/contentscript.js $DES/js/contentscript.js
-rm $DES/js/vapi-usercss.js
+rm $DES/js/vapi-usercss.pseudo.js
+rm $DES/js/vapi-usercss.real.js
 
 # Chrome store-specific
 cp -R $DES/_locales/nb $DES/_locales/no
diff --git a/tools/make-webext.sh b/tools/make-webext.sh
index 37a23b3a9..e7207b20d 100755
--- a/tools/make-webext.sh
+++ b/tools/make-webext.sh
@@ -28,14 +28,14 @@ cp platform/webext/manifest.json        $DES/
 cp platform/webext/polyfill.js          $DES/js/
 cp platform/webext/vapi-webrequest.js   $DES/js/
 cp platform/webext/vapi-cachestorage.js $DES/js/
-cp platform/webext/vapi-usercss.js      $DES/js/
 
 echo "*** uBlock0.webext: concatenating content scripts"
-cat $DES/js/vapi-usercss.js > /tmp/contentscript.js
+cat $DES/js/vapi-usercss.real.js > /tmp/contentscript.js
 echo >> /tmp/contentscript.js
 grep -v "^'use strict';$" $DES/js/contentscript.js >> /tmp/contentscript.js
 mv /tmp/contentscript.js $DES/js/contentscript.js
-rm $DES/js/vapi-usercss.js
+rm $DES/js/vapi-usercss.pseudo.js
+rm $DES/js/vapi-usercss.real.js
 
 # Webext-specific
 rm $DES/img/icon_128.png