diff --git a/css/leptonChrome.css b/css/leptonChrome.css
index 296b27c..aeea15e 100644
--- a/css/leptonChrome.css
+++ b/css/leptonChrome.css
@@ -4517,6 +4517,14 @@
     opacity: var(--tab-separator-opacity);
   }
 
+  @supports -moz-bool-pref("userChrome.tab.one_liner") {
+    @supports not -moz-bool-pref("userChrome.tab.one_liner.tabbar_first") {
+      .tabbrowser-tab:not([visuallyselected], [multiselected], :hover):first-child .tab-background::before {
+        opacity: var(--tab-separator-opacity);
+        transform: translateX(-1.5px) translateY(calc(-50% + 1px));
+      }
+    }
+  }
   @supports -moz-bool-pref("userChrome.tab.newtab_button_like_tab") {
     #tabs-newtab-button:not(:hover, [open])::before {
       opacity: var(--tab-separator-opacity);
diff --git a/src/tabbar/unselected_tab/_dynamic_separator.scss b/src/tabbar/unselected_tab/_dynamic_separator.scss
index 9633b1b..4088c02 100644
--- a/src/tabbar/unselected_tab/_dynamic_separator.scss
+++ b/src/tabbar/unselected_tab/_dynamic_separator.scss
@@ -57,6 +57,14 @@
 .tabbrowser-tab:not([visuallyselected], [multiselected], :hover, :first-child) .tab-background::before {
   opacity: var(--tab-separator-opacity);
 }
+@include Option("userChrome.tab.one_liner") {
+  @include NotOption("userChrome.tab.one_liner.tabbar_first") {
+    .tabbrowser-tab:not([visuallyselected], [multiselected], :hover):first-child .tab-background::before {
+      opacity: var(--tab-separator-opacity);
+      transform: translateX(-1.5px) translateY(calc(-50% + 1px));
+    }
+  }
+}
 @include Option("userChrome.tab.newtab_button_like_tab") {
   #tabs-newtab-button:not(:hover, [open])::before {
     opacity: var(--tab-separator-opacity);