diff --git a/browser/components/customizableui/CustomizeMode.sys.mjs b/browser/components/customizableui/CustomizeMode.sys.mjs
index 86c5e1b786b1ee788c95a1452d1e09b61062e27a..72888a7248e70b43dfbd62bd7972f9ead25d6c8b 100644
--- a/browser/components/customizableui/CustomizeMode.sys.mjs
+++ b/browser/components/customizableui/CustomizeMode.sys.mjs
@@ -27,7 +27,6 @@ const lazy = {};
 ChromeUtils.defineESModuleGetters(lazy, {
   AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
   DragPositionManager: "resource:///modules/DragPositionManager.sys.mjs",
-  SessionStore: "resource:///modules/sessionstore/SessionStore.sys.mjs",
   URILoadingHelper: "resource:///modules/URILoadingHelper.sys.mjs",
 });
 ChromeUtils.defineModuleGetter(
@@ -225,7 +224,6 @@ CustomizeMode.prototype = {
     gTab = aTab;
 
     gTab.setAttribute("customizemode", "true");
-    lazy.SessionStore.persistTabAttribute("customizemode");
 
     if (gTab.linkedPanel) {
       gTab.linkedBrowser.stop();
diff --git a/browser/components/sessionstore/SessionStore.sys.mjs b/browser/components/sessionstore/SessionStore.sys.mjs
index 2c50de65f83687bc27292bf1eb850e8d75ca6c9d..82e5b6748175523592bfc48d365f7d0d54be84ee 100644
--- a/browser/components/sessionstore/SessionStore.sys.mjs
+++ b/browser/components/sessionstore/SessionStore.sys.mjs
@@ -434,10 +434,6 @@ export var SessionStore = {
     SessionStoreInternal.deleteCustomGlobalValue(aKey);
   },
 
-  persistTabAttribute: function ss_persistTabAttribute(aName) {
-    SessionStoreInternal.persistTabAttribute(aName);
-  },
-
   restoreLastSession: function ss_restoreLastSession() {
     SessionStoreInternal.restoreLastSession();
   },
@@ -3615,12 +3611,6 @@ var SessionStoreInternal = {
     this.saveStateDelayed();
   },
 
-  persistTabAttribute: function ssi_persistTabAttribute(aName) {
-    if (lazy.TabAttributes.persist(aName)) {
-      this.saveStateDelayed();
-    }
-  },
-
   /**
    * Undoes the closing of a tab or window which corresponds
    * to the closedId passed in.
@@ -4782,13 +4772,6 @@ var SessionStoreInternal = {
       tab.updateLastAccessed(tabData.lastAccessed);
     }
 
-    if ("attributes" in tabData) {
-      // Ensure that we persist tab attributes restored from previous sessions.
-      Object.keys(tabData.attributes).forEach(a =>
-        lazy.TabAttributes.persist(a)
-      );
-    }
-
     if (!tabData.entries) {
       tabData.entries = [];
     }
diff --git a/browser/components/sessionstore/TabAttributes.sys.mjs b/browser/components/sessionstore/TabAttributes.sys.mjs
index 1c7f54b6abcbe4748617e1895640171d5f71b9c4..ea53156d129cba5309702446a3994747af81c069 100644
--- a/browser/components/sessionstore/TabAttributes.sys.mjs
+++ b/browser/components/sessionstore/TabAttributes.sys.mjs
@@ -2,27 +2,13 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-// We never want to directly read or write these attributes.
-// 'image' should not be accessed directly but handled by using the
-//         gBrowser.getIcon()/setIcon() methods.
-// 'muted' should not be accessed directly but handled by using the
-//         tab.linkedBrowser.audioMuted/toggleMuteAudio methods.
-// 'pending' is used internal by sessionstore and managed accordingly.
-const ATTRIBUTES_TO_SKIP = new Set([
-  "image",
-  "muted",
-  "pending",
-  "skipbackgroundnotify",
-]);
+// Tab attributes which are persisted & restored by SessionStore.
+const PERSISTED_ATTRIBUTES = ["customizemode"];
 
 // A set of tab attributes to persist. We will read a given list of tab
 // attributes when collecting tab data and will re-set those attributes when
 // the given tab data is restored to a new tab.
 export var TabAttributes = Object.freeze({
-  persist(name) {
-    return TabAttributesInternal.persist(name);
-  },
-
   get(tab) {
     return TabAttributesInternal.get(tab);
   },
@@ -33,21 +19,10 @@ export var TabAttributes = Object.freeze({
 });
 
 var TabAttributesInternal = {
-  _attrs: new Set(),
-
-  persist(name) {
-    if (this._attrs.has(name) || ATTRIBUTES_TO_SKIP.has(name)) {
-      return false;
-    }
-
-    this._attrs.add(name);
-    return true;
-  },
-
   get(tab) {
     let data = {};
 
-    for (let name of this._attrs) {
+    for (let name of PERSISTED_ATTRIBUTES) {
       if (tab.hasAttribute(name)) {
         data[name] = tab.getAttribute(name);
       }
@@ -57,15 +32,11 @@ var TabAttributesInternal = {
   },
 
   set(tab, data = {}) {
-    // Clear attributes.
-    for (let name of this._attrs) {
+    // Clear & Set attributes.
+    for (let name of PERSISTED_ATTRIBUTES) {
       tab.removeAttribute(name);
-    }
-
-    // Set attributes.
-    for (let [name, value] of Object.entries(data)) {
-      if (!ATTRIBUTES_TO_SKIP.has(name)) {
-        tab.setAttribute(name, value);
+      if (name in data) {
+        tab.setAttribute(name, data[name]);
       }
     }
   },
diff --git a/browser/components/sessionstore/test/browser_attributes.js b/browser/components/sessionstore/test/browser_attributes.js
index 336573a50862ab8ae271143762c439a977ed542e..db349a31a251420af6795b55c77dd91e8f6be965 100644
--- a/browser/components/sessionstore/test/browser_attributes.js
+++ b/browser/components/sessionstore/test/browser_attributes.js
@@ -38,45 +38,68 @@ add_task(async function test() {
   ok(tab.hasAttribute("muted"), "tab.muted exists");
 
   // Make sure we do not persist 'image' and 'muted' attributes.
-  ss.persistTabAttribute("image");
-  ss.persistTabAttribute("muted");
   let { attributes } = JSON.parse(ss.getTabState(tab));
   ok(!("image" in attributes), "'image' attribute not saved");
   ok(!("muted" in attributes), "'muted' attribute not saved");
-  ok(!("custom" in attributes), "'custom' attribute not saved");
-
-  // Test persisting a custom attribute.
-  tab.setAttribute("custom", "foobar");
-  ss.persistTabAttribute("custom");
-
-  ({ attributes } = JSON.parse(ss.getTabState(tab)));
-  is(attributes.custom, "foobar", "'custom' attribute is correct");
-
-  // Make sure we're backwards compatible and restore old 'image' attributes.
+  ok(!("customizemode" in attributes), "'customizemode' attribute not saved");
+
+  // Test persisting a customizemode attribute.
+  {
+    let customizationReady = BrowserTestUtils.waitForEvent(
+      gNavToolbox,
+      "customizationready"
+    );
+    gCustomizeMode.enter();
+    await customizationReady;
+  }
+
+  let customizeIcon = gBrowser.getIcon(gBrowser.selectedTab);
+  ({ attributes } = JSON.parse(ss.getTabState(gBrowser.selectedTab)));
+  ok(!("image" in attributes), "'image' attribute not saved");
+  is(attributes.customizemode, "true", "'customizemode' attribute is correct");
+
+  {
+    let afterCustomization = BrowserTestUtils.waitForEvent(
+      gNavToolbox,
+      "aftercustomization"
+    );
+    gCustomizeMode.exit();
+    await afterCustomization;
+  }
+
+  // Test restoring a customizemode tab.
   let state = {
-    entries: [{ url: "about:mozilla", triggeringPrincipal_base64 }],
-    attributes: { custom: "foobaz" },
-    image: gBrowser.getIcon(tab),
+    entries: [],
+    attributes: { customizemode: "true", nonpersisted: "true" },
   };
 
+  // Customize mode doesn't like being restored on top of a non-blank tab.
+  // For the moment, it appears it isn't possible to restore customizemode onto
+  // an existing non-blank tab outside of tests, however this may be a latent
+  // bug if we ever try to do that in the future.
+  let principal = Services.scriptSecurityManager.createNullPrincipal({});
+  tab.linkedBrowser.createAboutBlankContentViewer(principal, principal);
+
   // Prepare a pending tab waiting to be restored.
   let promise = promiseTabRestoring(tab);
   ss.setTabState(tab, JSON.stringify(state));
   await promise;
 
   ok(tab.hasAttribute("pending"), "tab is pending");
-  is(gBrowser.getIcon(tab), state.image, "tab has correct icon");
+  ok(tab.hasAttribute("customizemode"), "tab is in customizemode");
+  ok(!tab.hasAttribute("nonpersisted"), "tab has no nonpersisted attribute");
+  is(gBrowser.getIcon(tab), customizeIcon, "tab has correct icon");
   ok(!state.attributes.image, "'image' attribute not saved");
 
   // Let the pending tab load.
   gBrowser.selectedTab = tab;
-  await promiseTabRestored(tab);
 
   // Ensure no 'image' or 'pending' attributes are stored.
   ({ attributes } = JSON.parse(ss.getTabState(tab)));
   ok(!("image" in attributes), "'image' attribute not saved");
   ok(!("pending" in attributes), "'pending' attribute not saved");
-  is(attributes.custom, "foobaz", "'custom' attribute is correct");
+  ok(!("nonpersisted" in attributes), "'nonpersisted' attribute not saved");
+  is(attributes.customizemode, "true", "'customizemode' attribute is correct");
 
   // Clean up.
   gBrowser.removeTab(tab);