--- a/browser/themes/windows/compacttheme.css
+++ b/browser/themes/windows/compacttheme.css
@@ -2,16 +2,17 @@
 % 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/.
 
 %include ../shared/compacttheme.inc.css
 
 :root {
    /* Matches the #browser-border-start, #browser-border-end color */
   --chrome-nav-bar-separator-color: rgba(10, 31, 51, 0.35);
+  --chrome-tabs-border-color: hsla(240, 5%, 5%, 0.3);
 }
 
 /* The window background is white due to no accentcolor in the lightweight
    theme. It can't be changed to transparent when there is no compositor
    (Win 7 in classic / basic theme), or else dragging and focus become
    broken. So instead just show the normal titlebar in that case, and override
    the window color as transparent when the compositor is available. */
 @media (-moz-windows-compositor: 0) {
@@ -37,39 +38,26 @@
 @media (-moz-windows-glass) {
   .tabbrowser-tab {
     background-color: var(--chrome-background-color);
   }
 }
 
 @media (-moz-os-version: windows-win7),
        (-moz-os-version: windows-win8) {
-  /* It'd be nice if there was an element in the scrollbox's inner content
-     that collapsed to the current width of the tabs. Since there isn't we
-     need to handle overflowing and non-overflowing tabs separately.
-
-     In the case of overflowing tabs, set a border-top on the entire container,
-     otherwise we need to set it on each element individually */
-  #main-window[sizemode=normal] .tabbrowser-tabs[overflow="true"] {
-    background-clip: padding-box;
-    border-top: 1px solid var(--chrome-nav-bar-separator-color);
-    border-inline-end: 1px solid var(--chrome-nav-bar-separator-color);
+  #tabbrowser-tabs > .tabbrowser-tab > .tab-stack > .tab-background {
+    border-top: 1px solid var(--chrome-tabs-border-color);
   }
 
-  /* Add a border to the left of the first tab (or scroll arrow).  Using .tabbrowser-tabs
-     instead of #TabsToolbar because it will work even in customize mode. */
-  #main-window[sizemode=normal] .tabbrowser-tabs {
-    background-clip: padding-box;
-    border-inline-start: 1px solid var(--chrome-nav-bar-separator-color);
-    border-inline-end: 1px solid transparent;
+  #tabbrowser-tabs > .tabbrowser-tab[first-tab="true"] > .tab-stack > .tab-background {
+    border-inline-start: 1px solid var(--chrome-tabs-border-color) !important;
   }
 
-  #main-window[sizemode=normal] .tabbrowser-tabs:not([overflow="true"]) .closing-tabs-spacer {
-    background-clip: padding-box;
-    border-inline-start: 1px solid var(--chrome-nav-bar-separator-color);
+  #tabbrowser-tabs > .tabbrowser-tab[last-tab="true"] > .tab-stack > .tab-background {
+    border-inline-end: 1px solid var(--chrome-tabs-border-color) !important;
   }
 
   /* Use default window colors when in non-maximized mode */
   #tabbrowser-tabs,
   #TabsToolbar,
   #browser-panel,
   #titlebar-content {
     background: transparent;