--- a/browser/themes/shared/customizableui/panelUI.inc.css
+++ b/browser/themes/shared/customizableui/panelUI.inc.css
@@ -584,16 +584,17 @@ toolbarbutton[constrain-size="true"][cui
 #appMenu-tp-label {
   -moz-context-properties: fill;
   fill: currentColor;
   list-style-image: url(chrome://browser/skin/tracking-protection-16.svg#enabled);
   -moz-box-flex: 1;
 }
 
 #appMenu-tp-toggle {
+  -moz-appearance: none;
   box-sizing: border-box;
   min-width: 26px;
   height: 10px;
   border-radius: 10px;
   background-color: var(--arrowpanel-dimmed-even-further);
   border: 1px solid transparent;
   margin-top: 4px;
   margin-bottom: 4px;