--- a/browser/themes/windows/browser.css
+++ b/browser/themes/windows/browser.css
@@ -104,23 +104,16 @@ toolbar:-moz-lwtheme {
   margin-top: 3px;
 }
 
 #main-window[tabsintitlebar][sizemode="normal"]:not([inFullscreen])[chromehidden~="menubar"] #toolbar-menubar ~ #TabsToolbar,
 #main-window[tabsintitlebar][sizemode="normal"]:not([inFullscreen]) #toolbar-menubar[autohide="true"][inactive] ~ #TabsToolbar {
   margin-top: var(--space-above-tabbar);
 }
 
-#main-window[customize-entered][tabsintitlebar]:not([inFullscreen]) #toolbar-menubar[customizing-dragovertarget].customization-target::before,
-#main-window[customize-entered][tabsintitlebar]:not([inFullscreen]) #TabsToolbar[customizing-dragovertarget].customization-target::before,
-#main-window[customize-entered][tabsintitlebar]:not([inFullscreen]) #toolbar-menubar.customization-target:hover::before,
-#main-window[customize-entered][tabsintitlebar]:not([inFullscreen]) #TabsToolbar.customization-target:hover::before {
-  outline-color: CaptionText;
-}
-
 #navigator-toolbox {
   -moz-appearance: none;
   background-color: transparent;
   border-top: none;
 }
 
 #navigator-toolbox::after {
   content: "";