diff --git a/browser/base/content/tabbrowser.xml b/browser/base/content/tabbrowser.xml
index ce1b547f9c5358da0f3ed73021f14555c2f9eeb5..4062bfe50b68ed2e51a24e85388e7bf8aed133a7 100644
--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -7340,6 +7340,8 @@
                   class="tab-background">
           <xul:hbox xbl:inherits="selected=visuallyselected"
                     class="tab-line"/>
+          <xul:spacer flex="1"/>
+          <xul:hbox class="tab-bottom-line"/>
         </xul:vbox>
         <xul:hbox xbl:inherits="pinned,selected=visuallyselected,titlechanged,attention"
                   class="tab-content" align="center">
diff --git a/browser/components/contextualidentity/content/usercontext.css b/browser/components/contextualidentity/content/usercontext.css
index c95fba53933f3e272d311ae8f03fe13998bd6e54..540c1f9ced3b091abc714abbfa4eb1b8d6d96b98 100644
--- a/browser/components/contextualidentity/content/usercontext.css
+++ b/browser/components/contextualidentity/content/usercontext.css
@@ -100,10 +100,13 @@
   -moz-box-align: center;
 }
 
-.tabbrowser-tab[usercontextid] {
-  background-image: linear-gradient(to right, transparent 20%, var(--identity-tab-color) 30%, var(--identity-tab-color) 70%, transparent 80%);
-  background-size: auto 2px;
-  background-repeat: no-repeat;
+.tabbrowser-tab[usercontextid] > .tab-stack > .tab-background > .tab-bottom-line {
+  background: linear-gradient(to right, transparent 10%, var(--identity-tab-color) 10%, var(--identity-tab-color) 90%, transparent 90%);
+  height: 2px;
+}
+
+.tabbrowser-tab[pinned][usercontextid] > .tab-stack > .tab-background > .tab-bottom-line {
+  background: linear-gradient(to right, transparent 30%, var(--identity-tab-color) 30%, var(--identity-tab-color) 70%, transparent 70%);
 }
 
 .userContext-icon,