--- a/browser/components/customizableui/CustomizableUI.jsm
+++ b/browser/components/customizableui/CustomizableUI.jsm
@@ -325,16 +325,17 @@ var CustomizableUIInternal = {
 
     if (gPhotonStructure) {
       if (gAreas.has(CustomizableUI.AREA_PANEL)) {
         this.unregisterArea(CustomizableUI.AREA_PANEL, true);
       }
       this.registerArea(CustomizableUI.AREA_FIXED_OVERFLOW_PANEL, {
         type: CustomizableUI.TYPE_MENU_PANEL,
         defaultPlacements: [],
+        anchor: "nav-bar-overflow-button",
       }, true);
     } else {
       if (gAreas.has(CustomizableUI.AREA_FIXED_OVERFLOW_PANEL)) {
         this.unregisterArea(CustomizableUI.AREA_FIXED_OVERFLOW_PANEL, true);
       }
       // In tests we destroy some widgets. Those should be removed from the
       // default placements when re-registering the panel.
       let placementsToUse = Array.from(gDefaultPanelPlacements);