diff --git a/browser/components/customizableui/src/CustomizeMode.jsm b/browser/components/customizableui/src/CustomizeMode.jsm
index 4b4ba4c9d84a..9cb9da6e95bc 100644
--- a/browser/components/customizableui/src/CustomizeMode.jsm
+++ b/browser/components/customizableui/src/CustomizeMode.jsm
@@ -527,6 +527,11 @@ CustomizeMode.prototype = {
       aNode.removeAttribute("command");
     }
 
+    if (aNode.hasAttribute("observes")) {
+      wrapper.setAttribute("itemobserves", aNode.getAttribute("observes"));
+      aNode.removeAttribute("observes");
+    }
+
     if (aNode.checked) {
       wrapper.setAttribute("itemchecked", "true");
       aNode.checked = false;
@@ -602,6 +607,10 @@ CustomizeMode.prototype = {
       return null;
     }
 
+    if (aWrapper.hasAttribute("itemobserves")) {
+      toolbarItem.setAttribute("observes", aWrapper.getAttribute("itemobserves"));
+    }
+
     if (aWrapper.hasAttribute("itemchecked")) {
       toolbarItem.checked = true;
     }
diff --git a/browser/components/customizableui/test/browser.ini b/browser/components/customizableui/test/browser.ini
index 8db2b457a2e4..3a7dfad508bf 100644
--- a/browser/components/customizableui/test/browser.ini
+++ b/browser/components/customizableui/test/browser.ini
@@ -11,6 +11,7 @@ support-files =
 [browser_878452_drag_to_panel.js]
 [browser_880164_customization_context_menus.js]
 [browser_880382_drag_wide_widgets_in_panel.js]
+[browser_885052_customize_mode_observers_disabed.js]
 [browser_885530_showInPrivateBrowsing.js]
 [browser_886323_buildArea_removable_nodes.js]
 [browser_887438_currentset_shim.js]
diff --git a/browser/components/customizableui/test/browser_885052_customize_mode_observers_disabed.js b/browser/components/customizableui/test/browser_885052_customize_mode_observers_disabed.js
new file mode 100644
index 000000000000..1d9b88cf09f4
--- /dev/null
+++ b/browser/components/customizableui/test/browser_885052_customize_mode_observers_disabed.js
@@ -0,0 +1,37 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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/. */
+
+"use strict";
+
+// Observers should be disabled when in customization mode.
+add_task(function() {
+  BrowserFullScreen();
+  let shownPanelPromise = promisePanelShown(window);
+  PanelUI.toggle({type: "command"});
+  yield shownPanelPromise;
+
+  let fullscreenButton = document.getElementById("fullscreen-button");
+  ok(fullscreenButton.checked, "Fullscreen button should be checked when in fullscreen.")
+
+  yield startCustomizing();
+
+  let fullscreenButtonWrapper = document.getElementById("wrapper-fullscreen-button");
+  ok(fullscreenButtonWrapper.hasAttribute("itemobserves"), "Observer should be moved to wrapper");
+  fullscreenButton = document.getElementById("fullscreen-button");
+  ok(!fullscreenButton.hasAttribute("observes"), "Observer should be removed from button");
+  ok(!fullscreenButton.checked, "Fullscreen button should no longer be checked during customization mode");
+
+  yield endCustomizing();
+  BrowserFullScreen();
+  shownPanelPromise = promisePanelShown(window);
+  PanelUI.toggle({type: "command"});
+  yield shownPanelPromise;
+
+  fullscreenButton = document.getElementById("fullscreen-button");
+  ok(!fullscreenButton.checked, "Fullscreen button should not be checked when not in fullscreen.")
+
+  let hiddenPanelPromise = promisePanelHidden(window);
+  PanelUI.toggle({type: "command"});
+  yield hiddenPanelPromise;
+});