diff --git a/browser/themes/shared/tabs.css b/browser/themes/shared/tabs.css
index eb92f71e5942a19618fd74492354de78ac03bacf..0ba9a169b1a8937e8cdf39fa1fe8e5f14e09c306 100644
--- a/browser/themes/shared/tabs.css
+++ b/browser/themes/shared/tabs.css
@@ -633,7 +633,7 @@
   toolbarbutton:not(#firefox-view-button),
   toolbarpaletteitem:not(#wrapper-firefox-view-button)
 ) + #tabbrowser-tabs {
-  border-inline-start: 1px solid color-mix(in srgb, currentColor 25%, transparent);
+  border-inline-start: transparent;
   padding-inline-start: calc(var(--tab-overflow-pinned-tabs-width) + 2px);
   margin-inline-start: 2px;
 }