--- a/browser/components/customizableui/CustomizableUI.jsm
+++ b/browser/components/customizableui/CustomizableUI.jsm
@@ -4114,17 +4114,19 @@ OverflowableToolbar.prototype = {
 
   show() {
     if (this._panel.state == "open") {
       return Promise.resolve();
     }
     return new Promise(resolve => {
       let doc = this._panel.ownerDocument;
       this._panel.hidden = false;
-      let contextMenu = doc.getElementById(this._panel.getAttribute("context"));
+      let mainViewId = this._panel.querySelector("panelmultiview").getAttribute("mainViewId");
+      let mainView = doc.getElementById(mainViewId);
+      let contextMenu = doc.getElementById(mainView.getAttribute("context"));
       gELS.addSystemEventListener(contextMenu, "command", this, true);
       let anchor = doc.getAnonymousElementByAttribute(this._chevron, "class", "toolbarbutton-icon");
       this._panel.openPopup(anchor || this._chevron);
       this._chevron.open = true;
 
       let overflowableToolbarInstance = this;
       this._panel.addEventListener("popupshown", function(aEvent) {
         this.addEventListener("dragover", overflowableToolbarInstance);

--- a/browser/components/customizableui/content/panelUI.inc.xul
+++ b/browser/components/customizableui/content/panelUI.inc.xul
@@ -372,21 +372,21 @@
               label="&customizeMenu.addMoreItems.label;"/>
   </menupopup>
 </panel>
 
 <panel id="widget-overflow"
        role="group"
        type="arrow"
        noautofocus="true"
-       context="toolbar-context-menu"
        position="bottomcenter topright"
        hidden="true">
   <panelmultiview mainViewId="widget-overflow-mainView">
-    <panelview id="widget-overflow-mainView">
+    <panelview id="widget-overflow-mainView"
+               context="toolbar-context-menu">
       <vbox id="widget-overflow-scroller">
         <vbox id="widget-overflow-list" class="widget-overflow-list"
               overflowfortoolbar="nav-bar"/>
       </vbox>
     </panelview>
   </panelmultiview>
 </panel>