diff --git a/platform/mv3/extension/js/scripting/css-generic.js b/platform/mv3/extension/js/scripting/css-generic.js
index 52c3781a2..7a7ed0c5e 100644
--- a/platform/mv3/extension/js/scripting/css-generic.js
+++ b/platform/mv3/extension/js/scripting/css-generic.js
@@ -74,7 +74,7 @@ const hashFromStr = (type, s) => {
 // http://www.w3.org/TR/2014/REC-html5-20141028/infrastructure.html#space-separated-tokens
 // http://jsperf.com/enumerate-classes/6
 
-const uBOL_idFromNode = (node, out) => {
+const uBOL_idFromNode = node => {
     const raw = node.id;
     if ( typeof raw !== 'string' || raw.length === 0 ) { return; }
     const hash = hashFromStr(0x23 /* '#' */, raw.trim());
@@ -82,15 +82,15 @@ const uBOL_idFromNode = (node, out) => {
     if ( selectorList === undefined ) { return; }
     genericSelectorMap.delete(hash);
     if ( genericExceptionSieve.has(hash) ) {
-        applyExceptions(selectorList, out);
+        applyExceptions(selectorList);
     } else {
-        out.push(selectorList);
+        styleSheetSelectors.push(selectorList);
     }
 };
 
 // https://github.com/uBlockOrigin/uBlock-issues/discussions/2076
 //   Performance: avoid using Element.classList
-const uBOL_classesFromNode = (node, out) => {
+const uBOL_classesFromNode = node => {
     const s = node.getAttribute('class');
     if ( typeof s !== 'string' ) { return; }
     const len = s.length;
@@ -106,14 +106,14 @@ const uBOL_classesFromNode = (node, out) => {
         if ( selectorList === undefined ) { continue; }
         genericSelectorMap.delete(hash);
         if ( genericExceptionSieve.has(hash) ) {
-            applyExceptions(selectorList, out);
+            applyExceptions(selectorList);
         } else {
-            out.push(selectorList);
+            styleSheetSelectors.push(selectorList);
         }
     }
 };
 
-const applyExceptions = (selectorList, out) => {
+const applyExceptions = selectorList => {
     const selectors = new Set(selectorList.split(',\n'));
     self.isolatedAPI.forEachHostname(hostname => {
         const exceptions = genericExceptionMap.get(hostname);
@@ -124,7 +124,7 @@ const applyExceptions = (selectorList, out) => {
         if ( selectors.size === 0 ) { return true; }
     }, { hasEntities: true });
     if ( selectors.size === 0 ) { return; }
-    out.push(Array.from(selectors).join(',\n'));
+    styleSheetSelectors.push(Array.from(selectors).join(',\n'));
 }
 
 /******************************************************************************/
@@ -138,9 +138,7 @@ const pendingNodes = {
     next(out) {
         for ( const added of this.addedNodes ) {
             if ( this.nodeSet.has(added) ) { continue; }
-            if ( added.nodeType === 1 ) {
-                this.nodeSet.add(added);
-            }
+            this.nodeSet.add(added);
             if ( added.firstElementChild === null ) { continue; }
             for ( const descendant of added.querySelectorAll('[id],[class]') ) {
                 this.nodeSet.add(descendant);
@@ -168,8 +166,8 @@ const uBOL_processNodes = ( ) => {
         pendingNodes.next(nodes);
         if ( nodes.length === 0 ) { break; }
         for ( const node of nodes ) {
-            uBOL_idFromNode(node, styleSheetSelectors);
-            uBOL_classesFromNode(node, styleSheetSelectors);
+            uBOL_idFromNode(node);
+            uBOL_classesFromNode(node);
         }
         nodes.length = 0;
         if ( performance.now() >= deadline ) { break; }
@@ -196,14 +194,22 @@ const uBOL_processNodes = ( ) => {
 /******************************************************************************/
 
 const uBOL_processChanges = mutations => {
-    for ( let i = 0; i < mutations.length; i++ ) {
-        const mutation = mutations[i];
-        for ( const added of mutation.addedNodes ) {
-            if ( added.nodeType !== 1 ) { continue; }
-            pendingNodes.add(added);
+    for ( const mutation of mutations ) {
+        if ( mutation.type === 'childList' ) {
+            for ( const added of mutation.addedNodes ) {
+                if ( added.nodeType !== 1 ) { continue; }
+                if ( added.parentElement === null ) { continue; }
+                pendingNodes.add(added);
+            }
+        } else if ( mutation.attributeName === 'class' ) {
+            uBOL_classesFromNode(mutation.target);
+        } else {
+            uBOL_idFromNode(mutation.target);
         }
     }
-    if ( pendingNodes.hasNodes() === false ) { return; }
+    if ( pendingNodes.hasNodes() === false ) {
+        if ( styleSheetSelectors.length === 0 ) { return; }
+    }
     lastDomChange = Date.now();
     if ( processTimer !== undefined ) { return; }
     processTimer = self.setTimeout(( ) => {
@@ -227,11 +233,14 @@ const stopAll = ( ) => {
 
 /******************************************************************************/
 
-pendingNodes.add(document);
+if ( document.documentElement === null ) { return; }
+pendingNodes.add(document.documentElement);
 uBOL_processNodes();
 
 let domMutationObserver = new MutationObserver(uBOL_processChanges);
 domMutationObserver.observe(document, {
+    attributeFilter: [ 'class', 'id' ],
+    attributes: true,
     childList: true,
     subtree: true,
 });