diff --git a/platform/chromium/vapi-background.js b/platform/chromium/vapi-background.js
index a0efabb61..e7158af6b 100644
--- a/platform/chromium/vapi-background.js
+++ b/platform/chromium/vapi-background.js
@@ -54,6 +54,13 @@ if (
     });
 }
 
+// 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;
+
 var noopFunc = function(){};
 
 /******************************************************************************/
@@ -730,12 +737,7 @@ vAPI.messaging.onPortMessage = (function() {
     var messaging = vAPI.messaging,
         toAuxPending = {};
 
-    // https://issues.adblockplus.org/ticket/5695
-    // - Good idea, adopted: cleaner way to detect user-stylesheet support.
-    var supportsUserStylesheets = 
-        chrome.extensionTypes instanceof Object &&
-        chrome.extensionTypes.CSSOrigin instanceof Object &&
-        'USER' in chrome.extensionTypes.CSSOrigin;
+    var supportsUserStylesheets = vAPI.supportsUserStylesheets;
 
     // Use a wrapper to avoid closure and to allow reuse.
     var CallbackWrapper = function(port, request, timeout) {
diff --git a/src/js/reverselookup-worker.js b/src/js/reverselookup-worker.js
index aea180856..71c272014 100644
--- a/src/js/reverselookup-worker.js
+++ b/src/js/reverselookup-worker.js
@@ -98,7 +98,8 @@ var fromNetFilter = function(details) {
 var fromCosmeticFilter = function(details) {
     var match = /^#@?#/.exec(details.rawFilter),
         prefix = match[0],
-        filter = details.rawFilter.slice(prefix.length);
+        filter = details.rawFilter.slice(prefix.length),
+        selector = filter;
 
     // With low generic simple cosmetic filters, the class or id prefix
     // character is not part of the compiled data. So we must be ready to
@@ -173,28 +174,29 @@ var fromCosmeticFilter = function(details) {
             switch ( fargs[0] ) {
             case 0: // id-based
             case 2: // class-based
-                found = prefix + idOrClassPrefix + filter;
+                found = prefix + selector;
                 break;
             case 4:
             case 5:
             case 7:
-                found = prefix + filter;
+                found = prefix + selector;
                 break;
             case 1:
             case 3:
-                if ( fargs[2] === filter ) {
-                    found = prefix + filter;
+                if ( fargs[2] === selector ) {
+                    found = prefix + selector;
                 }
                 break;
             case 6:
             case 8:
             case 9:
+                if ( fargs[3] !== selector ) { break; }
                 if (
                     fargs[2] === '' ||
                     reHostname.test(fargs[2]) === true ||
                     reEntity !== undefined && reEntity.test(fargs[2]) === true
                 ) {
-                    found = fargs[2] + prefix + filter;
+                    found = fargs[2] + prefix + selector;
                 }
                 break;
             }