diff --git a/platform/mv3/extension/js/background.js b/platform/mv3/extension/js/background.js
index 1036e633b..d83abf48e 100644
--- a/platform/mv3/extension/js/background.js
+++ b/platform/mv3/extension/js/background.js
@@ -154,6 +154,17 @@ async function onPermissionsAdded(permissions) {
     }
 }
 
+async function onPermissionsChanged(op, permissions) {
+    await isFullyInitialized;
+    const { pending } = onPermissionsChanged;
+    await Promise.all(pending);
+    const promise = op === 'removed'
+        ? onPermissionsRemoved()
+        : onPermissionsAdded(permissions);
+    pending.push(promise);
+}
+onPermissionsChanged.pending = [];
+
 /******************************************************************************/
 
 function setDeveloperMode(state) {
@@ -698,13 +709,13 @@ runtime.onMessage.addListener((request, sender, callback) => {
 
 browser.permissions.onRemoved.addListener((...args) => {
     isFullyInitialized.then(( ) => {
-        onPermissionsRemoved(...args);
+        onPermissionsChanged('removed', ...args);
     });
 });
 
 browser.permissions.onAdded.addListener((...args) => {
     isFullyInitialized.then(( ) => {
-        onPermissionsAdded(...args);
+        onPermissionsChanged('added', ...args);
     });
 });
 
diff --git a/platform/mv3/extension/js/mode-manager.js b/platform/mv3/extension/js/mode-manager.js
index 1190cd216..4367ff6c2 100644
--- a/platform/mv3/extension/js/mode-manager.js
+++ b/platform/mv3/extension/js/mode-manager.js
@@ -365,17 +365,15 @@ export async function syncWithBrowserPermissions() {
     if ( afterMode > MODE_BASIC ) { return afterMode !== beforeMode; }
     const filteringModes = await getFilteringModeDetails();
     if ( allowedHostnames.has('all-urls') === false ) {
-        const { optimal, complete } = filteringModes;
-        for ( const hn of optimal ) {
-            if ( allowedHostnames.has(hn) ) { continue; }
-            if ( isDescendantHostnameOfIter(hn, allowedHostnames) ) { continue; }
-            optimal.delete(hn);
+        const { none, basic, optimal, complete } = filteringModes;
+        for ( const hn of new Set([ ...optimal, ...complete ]) ) {
+            applyFilteringMode(filteringModes, hn, afterMode);
             modified = true;
         }
-        for ( const hn of complete ) {
-            if ( allowedHostnames.has(hn) ) { continue; }
-            if ( isDescendantHostnameOfIter(hn, allowedHostnames) ) { continue; }
-            complete.delete(hn);
+        for ( const hn of allowedHostnames ) {
+            if ( optimal.has(hn) || complete.has(hn) ) { continue; }
+            if ( basic.has(hn) || none.has(hn) ) { continue; }
+            applyFilteringMode(filteringModes, hn, MODE_OPTIMAL);
             modified = true;
         }
         if ( modified ) {
diff --git a/platform/mv3/extension/js/utils.js b/platform/mv3/extension/js/utils.js
index 730325e1f..cab0b972a 100644
--- a/platform/mv3/extension/js/utils.js
+++ b/platform/mv3/extension/js/utils.js
@@ -105,10 +105,10 @@ const subtractHostnameIters = (itera, iterb) => {
 
 /******************************************************************************/
 
-const matchFromHostname = hn =>
+export const matchFromHostname = hn =>
     hn === '*' || hn === 'all-urls' ? '<all_urls>' : `*://*.${hn}/*`;
 
-const matchesFromHostnames = hostnames => {
+export const matchesFromHostnames = hostnames => {
     const out = [];
     for ( const hn of hostnames ) {
         out.push(matchFromHostname(hn));
@@ -116,20 +116,25 @@ const matchesFromHostnames = hostnames => {
     return out;
 };
 
-const hostnamesFromMatches = origins => {
+export const hostnameFromMatch = origin => {
+    if ( origin === '<all_urls>' || origin === '*://*/*' ) { return 'all-urls'; }
+    const match = reOriginToHostname.exec(origin);
+    if ( match === null ) { return ''; }
+    return match[1];
+};
+
+export const hostnamesFromMatches = origins => {
     const out = [];
     for ( const origin of origins ) {
-        if ( origin === '<all_urls>' || origin === '*://*/*' ) {
-            out.push('all-urls');
-            continue;
-        }
-        const match = /^\*:\/\/(?:\*\.)?([^/]+)\/\*/.exec(origin);
-        if ( match === null ) { continue; }
-        out.push(match[1]);
+        const hn = hostnameFromMatch(origin);
+        if ( hn === '' ) { continue; }
+        out.push(hn);
     }
     return out;
 };
 
+const reOriginToHostname = /^\*:\/\/(?:\*\.)?([^/]+)\/\*/;
+
 /******************************************************************************/
 
 const broadcastMessage = message => {
@@ -217,9 +222,6 @@ export {
     isDescendantHostnameOfIter,
     intersectHostnameIters,
     subtractHostnameIters,
-    matchFromHostname,
-    matchesFromHostnames,
-    hostnamesFromMatches,
     hasBroadHostPermissions,
     gotoURL,
     strArrayEq,