--- a/browser/themes/shared/tabs.inc.css
+++ b/browser/themes/shared/tabs.inc.css
@@ -300,16 +300,18 @@ tabbrowser {
 .tab-label {
   margin-inline-end: 0;
   margin-inline-start: 0;
 }
 
 .tab-close-button {
   margin-inline-end: -2px;
   padding: 0;
+  -moz-context-properties: fill, fill-opacity, stroke-opacity;
+  stroke-opacity: var(--toolbarbutton-icon-fill-opacity);
 }
 
 :root[uidensity=touch] .tab-close-button {
   margin-inline-end: -@horizontalTabPadding@;
   padding: 10px calc(@horizontalTabPadding@ - 2px);
 }
 
 .tab-icon-sound {

--- a/toolkit/themes/shared/icons/close.svg
+++ b/toolkit/themes/shared/icons/close.svg
@@ -1,7 +1,7 @@
 <!-- This Source Code Form is subject to the terms of the Mozilla Public
    - License, v. 2.0. If a copy of the MPL was not distributed with this
    - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
 <svg xmlns="http://www.w3.org/2000/svg" width="20" height="20">
   <path fill="context-fill" fill-opacity="context-fill-opacity" d="M0 0h20v20H0z"/>
-  <path fill="context-fill" d="M11.06 10l3.47-3.47a.75.75 0 0 0-1.06-1.06L10 8.94 6.53 5.47a.75.75 0 1 0-1.06 1.06L8.94 10l-3.47 3.47a.75.75 0 1 0 1.06 1.06L10 11.06l3.47 3.47a.75.75 0 0 0 1.06-1.06z"/>
+  <path fill="context-fill" fill-opacity="context-stroke-opacity" d="M11.06 10l3.47-3.47a.75.75 0 0 0-1.06-1.06L10 8.94 6.53 5.47a.75.75 0 1 0-1.06 1.06L8.94 10l-3.47 3.47a.75.75 0 1 0 1.06 1.06L10 11.06l3.47 3.47a.75.75 0 0 0 1.06-1.06z"/>
 </svg>