diff --git a/src/browser/base/content/ZenStartup.mjs b/src/browser/base/content/ZenStartup.mjs
index d00f5ed05..d0fc2758f 100644
--- a/src/browser/base/content/ZenStartup.mjs
+++ b/src/browser/base/content/ZenStartup.mjs
@@ -1,6 +1,5 @@
 {
   const lazy = {};
-  XPCOMUtils.defineLazyPreferenceGetter(lazy, 'sidebarHeightThrottle', 'zen.view.sidebar-height-throttle', 500);
   var ZenStartup = {
     init() {
       this.logHeader();
@@ -41,51 +40,13 @@
         gZenVerticalTabsManager.init();
         gZenCompactModeManager.init();
 
-        XPCOMUtils.defineLazyPreferenceGetter(
-          this,
-          'contentElementSeparation',
-          'zen.theme.content-element-separation',
-          0
-        );
-
         document.l10n.setAttributes(document.getElementById('tabs-newtab-button'), 'tabs-toolbar-new-tab');
-
-        function throttle(f, delay) {
-          let timer = 0;
-          return function (...args) {
-            clearTimeout(timer);
-            timer = setTimeout(() => f.apply(this, args), delay);
-          };
-        }
-
-        new ResizeObserver(throttle(this._updateTabsToolbar.bind(this), lazy.sidebarHeightThrottle)).observe(
-          document.getElementById('tabbrowser-tabs')
-        );
       } catch (e) {
         console.error('ZenThemeModifier: Error initializing browser layout', e);
       }
       this.closeWatermark();
     },
 
-    _updateTabsToolbar() {
-      // Set tabs max-height to the "toolbar-items" height
-      const toolbarItems = document.getElementById('tabbrowser-tabs');
-      const tabs = document.getElementById('tabbrowser-arrowscrollbox');
-      tabs.style.maxHeight = '0px'; // reset to 0
-      const toolbarRect = toolbarItems.getBoundingClientRect();
-      let height = toolbarRect.height;
-      // -5 for the controls padding
-      let totalHeight = toolbarRect.height - (this.contentElementSeparation * 2) - 5;
-      // remove the height from other elements that aren't hidden
-      const otherElements = document.querySelectorAll('#tabbrowser-tabs > *:not([hidden="true"])');
-      for (let tab of otherElements) {
-        if (tabs === tab) continue;
-        totalHeight -= tab.getBoundingClientRect().height;
-      }
-      tabs.style.maxHeight = totalHeight + 'px';
-      //console.info('ZenThemeModifier: set tabs max-height to', totalHeight + 'px');
-    },
-
     openWatermark() {
       if (!Services.prefs.getBoolPref('zen.watermark.enabled', false)) {
         return;
diff --git a/src/browser/base/content/ZenUIManager.mjs b/src/browser/base/content/ZenUIManager.mjs
index 93f2d2abe..235b830a3 100644
--- a/src/browser/base/content/ZenUIManager.mjs
+++ b/src/browser/base/content/ZenUIManager.mjs
@@ -5,6 +5,45 @@ var gZenUIManager = {
   init() {
     document.addEventListener('popupshowing', this.onPopupShowing.bind(this));
     document.addEventListener('popuphidden', this.onPopupHidden.bind(this));
+    XPCOMUtils.defineLazyPreferenceGetter(this, 'sidebarHeightThrottle', 'zen.view.sidebar-height-throttle', 500);
+    XPCOMUtils.defineLazyPreferenceGetter(
+      this,
+      'contentElementSeparation',
+      'zen.theme.content-element-separation',
+      0
+    );
+    
+    function throttle(f, delay) {
+      let timer = 0;
+      return function (...args) {
+        clearTimeout(timer);
+        timer = setTimeout(() => f.apply(this, args), delay);
+      };
+    }
+
+    new ResizeObserver(throttle(this.updateTabsToolbar.bind(this), this.sidebarHeightThrottle)).observe(
+      document.getElementById('tabbrowser-tabs')
+    );
+  },
+
+
+  updateTabsToolbar() {
+    // Set tabs max-height to the "toolbar-items" height
+    const toolbarItems = document.getElementById('tabbrowser-tabs');
+    const tabs = document.getElementById('tabbrowser-arrowscrollbox');
+    tabs.style.maxHeight = '0px'; // reset to 0
+    const toolbarRect = toolbarItems.getBoundingClientRect();
+    let height = toolbarRect.height;
+    // -5 for the controls padding
+    let totalHeight = toolbarRect.height - (this.contentElementSeparation * 2) - 5;
+    // remove the height from other elements that aren't hidden
+    const otherElements = document.querySelectorAll('#tabbrowser-tabs > *:not([hidden="true"])');
+    for (let tab of otherElements) {
+      if (tabs === tab) continue;
+      totalHeight -= tab.getBoundingClientRect().height;
+    }
+    tabs.style.maxHeight = totalHeight + 'px';
+    //console.info('ZenThemeModifier: set tabs max-height to', totalHeight + 'px');
   },
 
   openAndChangeToTab(url, options) {
diff --git a/src/browser/base/zen-components/ZenWorkspaces.mjs b/src/browser/base/zen-components/ZenWorkspaces.mjs
index 3c4198a13..7765f4d5d 100644
--- a/src/browser/base/zen-components/ZenWorkspaces.mjs
+++ b/src/browser/base/zen-components/ZenWorkspaces.mjs
@@ -1160,6 +1160,7 @@ var ZenWorkspaces = new (class extends ZenMultiWindowFeature {
     await this._updateWorkspacesChangeContextMenu();
 
     document.getElementById('tabbrowser-tabs')._positionPinnedTabs();
+    gZenUIManager.updateTabsToolbar();
 
     await this._propagateWorkspaceData({clearCache: onInit});
     for (let listener of this._changeListeners ?? []) {