--- a/browser/components/customizableui/CustomizableUI.jsm
+++ b/browser/components/customizableui/CustomizableUI.jsm
@@ -1673,18 +1673,16 @@ var CustomizableUIInternal = {
     // whether we're in an input container (text field)
     let inInput = false;
     // whether we're in a popup/context menu
     let inMenu = false;
     // whether we're in a toolbarbutton/toolbaritem
     let inItem = false;
     // whether the current menuitem has a valid closemenu attribute
     let menuitemCloseMenu = "auto";
-    // whether the toolbarbutton/item has a valid closemenu attribute.
-    let closemenu = "auto";
 
     // While keeping track of that, we go from the original target back up,
     // to the panel if we have to. We bail as soon as we find an input,
     // a toolbarbutton/item, or the panel:
     while (true && target) {
       // Skip out of iframes etc:
       if (target.nodeType == target.DOCUMENT_NODE) {
         if (!target.defaultView) {
@@ -1700,21 +1698,16 @@ var CustomizableUIInternal = {
           break;
         }
       }
       let tagName = target.localName;
       inInput = tagName == "input" || tagName == "textbox";
       inItem = tagName == "toolbaritem" || tagName == "toolbarbutton";
       let isMenuItem = tagName == "menuitem";
       inMenu = inMenu || isMenuItem;
-      if (inItem && target.hasAttribute("closemenu")) {
-        let closemenuVal = target.getAttribute("closemenu");
-        closemenu = (closemenuVal == "single" || closemenuVal == "none") ?
-                    closemenuVal : "auto";
-      }
 
       if (isMenuItem && target.hasAttribute("closemenu")) {
         let closemenuVal = target.getAttribute("closemenu");
         menuitemCloseMenu = (closemenuVal == "single" || closemenuVal == "none") ?
                             closemenuVal : "auto";
       }
       // Break out of the loop immediately for disabled items, as we need to
       // keep the menu open in that case.
@@ -1748,27 +1741,16 @@ var CustomizableUIInternal = {
       // Otherwise, we're probably fine to close the panel
       return false;
     }
     // If we're not in a menu, and we *are* in a type="menu" toolbarbutton,
     // we'll now interact with the menu
     if (inItem && target.getAttribute("type") == "menu") {
       return true;
     }
-    // If we're not in a menu, and we *are* in a type="menu-button" toolbarbutton,
-    // it depends whether we're in the dropmarker or the 'real' button:
-    if (inItem && target.getAttribute("type") == "menu-button") {
-      // 'real' button (which has a single action):
-      if (target.getAttribute("anonid") == "button") {
-        return closemenu != "none";
-      }
-      // otherwise, this is the outer button, and the user will now
-      // interact with the menu:
-      return true;
-    }
     return inInput || !inItem;
   },
 
   hidePanelForNode(aNode) {
     let panel = this._getPanelForNode(aNode);
     if (panel) {
       panel.hidePopup();
     }

--- a/browser/components/customizableui/test/browser_940307_panel_click_closure_handling.js
+++ b/browser/components/customizableui/test/browser_940307_panel_click_closure_handling.js
@@ -18,61 +18,16 @@ add_task(async function plain_button() {
   await document.getElementById("nav-bar").overflowable.show();
   let hiddenAgain = promiseOverflowHidden(window);
   EventUtils.synthesizeMouseAtCenter(button, {});
   await hiddenAgain;
   CustomizableUI.removeWidgetFromArea(button.id);
   button.remove();
 });
 
-/* Clicking a menu button should close the panel, opening the popup shouldn't.  */
-add_task(async function menu_button_popup() {
-  menuButton = document.createElement("toolbarbutton");
-  menuButton.setAttribute("type", "menu-button");
-  menuButton.id = "browser_940307_menubutton";
-  menuButton.setAttribute("label", "Menu button");
-
-  let menuPopup = document.createElement("menupopup");
-  menuPopup.id = "browser_940307_menupopup";
-
-  let menuItem = document.createElement("menuitem");
-  menuItem.setAttribute("label", "Menu item");
-  menuItem.id = "browser_940307_menuitem";
-
-  menuPopup.appendChild(menuItem);
-  menuButton.appendChild(menuPopup);
-  gNavToolbox.palette.appendChild(menuButton);
-  CustomizableUI.addWidgetToArea(menuButton.id, CustomizableUI.AREA_FIXED_OVERFLOW_PANEL);
-
-  await waitForOverflowButtonShown();
-
-  await document.getElementById("nav-bar").overflowable.show();
-  let hiddenAgain = promiseOverflowHidden(window);
-  let innerButton = document.getAnonymousElementByAttribute(menuButton, "anonid", "button");
-  EventUtils.synthesizeMouseAtCenter(innerButton, {});
-  await hiddenAgain;
-
-  // Now click the dropmarker to show the menu
-  await document.getElementById("nav-bar").overflowable.show();
-  hiddenAgain = promiseOverflowHidden(window);
-  let menuShown = promisePanelElementShown(window, menuPopup);
-  let dropmarker = document.getAnonymousElementByAttribute(menuButton, "type", "menu-button");
-  EventUtils.synthesizeMouseAtCenter(dropmarker, {});
-  await menuShown;
-  // Panel should stay open:
-  ok(isOverflowOpen(), "Panel should still be open");
-  let menuHidden = promisePanelElementHidden(window, menuPopup);
-  // Then click the menu item to close all the things
-  EventUtils.synthesizeMouseAtCenter(menuItem, {});
-  await menuHidden;
-  await hiddenAgain;
-  CustomizableUI.removeWidgetFromArea(menuButton.id);
-  menuButton.remove();
-});
-
 add_task(async function searchbar_in_panel() {
   CustomizableUI.addWidgetToArea("search-container",
                                  CustomizableUI.AREA_FIXED_OVERFLOW_PANEL);
 
   await waitForOverflowButtonShown();
 
   await document.getElementById("nav-bar").overflowable.show();
 

--- a/browser/themes/shared/customizableui/customizeMode.inc.css
+++ b/browser/themes/shared/customizableui/customizeMode.inc.css
@@ -197,28 +197,26 @@ toolbarpaletteitem[notransition].panel-c
 toolbarpaletteitem[notransition][place="toolbar"],
 toolbarpaletteitem[notransition][place="palette"],
 toolbarpaletteitem[notransition][place="panel"] {
   transition: none;
 }
 
 toolbarpaletteitem > toolbarbutton > .toolbarbutton-icon,
 toolbarpaletteitem > toolbarbutton > .toolbarbutton-badge-stack > .toolbarbutton-icon,
-toolbarpaletteitem > toolbaritem.panel-wide-item,
-toolbarpaletteitem > toolbarbutton[type="menu-button"] {
+toolbarpaletteitem > toolbaritem.panel-wide-item {
   transition: transform var(--drag-drop-transition-duration) cubic-bezier(.6, 2, .75, 1.5) !important;
 }
 
 toolbarpaletteitem[mousedown] > toolbarbutton > .toolbarbutton-icon,
 toolbarpaletteitem[mousedown] > toolbarbutton > .toolbarbutton-badge-stack > .toolbarbutton-icon {
   transform: scale(1.3);
 }
 
-toolbarpaletteitem[mousedown] > toolbaritem.panel-wide-item,
-toolbarpaletteitem[mousedown] > toolbarbutton[type="menu-button"] {
+toolbarpaletteitem[mousedown] > toolbaritem.panel-wide-item {
   transform: scale(1.1);
 }
 
 /* Override the toolkit styling for items being dragged over. */
 toolbarpaletteitem[place="toolbar"] {
   border-left-width: 0;
   border-right-width: 0;
   margin-right: 0;