--- a/browser/themes/shared/customizableui/customizeMode.inc.css
+++ b/browser/themes/shared/customizableui/customizeMode.inc.css
@@ -34,16 +34,17 @@
   margin-left: 2em;
   margin-right: 2em;
 }
 
 #main-window:-moz-any([customize-entering],[customize-exiting]) #tab-view-deck {
   pointer-events: none;
 }
 
+%ifndef MOZ_PHOTON_THEME
 #main-window[customize-entered] .customization-target:not(:-moz-any(#PanelUI-contents, #TabsToolbar, #toolbar-menubar))::before,
 #PanelUI-contents > .panel-customization-placeholder {
   -moz-outline-radius: 2.5px;
   outline: 1px dashed transparent;
 }
 
 #main-window[customize-entered] .customization-target:not(:-moz-any(#PanelUI-contents, #TabsToolbar, #toolbar-menubar))::before {
   /* Prevent jumping of tabs when switching a window between inactive and active (bug 853415). */
@@ -90,18 +91,19 @@
   transition: outline-color 250ms linear;
   outline-color: var(--panel-separator-color);
 }
 
 #PanelUI-contents > .panel-customization-placeholder {
   cursor: auto;
   outline-offset: -5px;
 }
+%endif
 
-#main-window[customizing] .customization-target:not(#PanelUI-contents) {
+#main-window[customizing] .customization-target:not(#PanelUI-contents):not(#widget-overflow-fixed-list) {
   min-width: 100px;
   padding-left: 10px;
   padding-right: 10px;
 }
 
 #customization-container {
   background-color: -moz-field;
   color: -moz-fieldText;