diff --git a/css/leptonChrome.css b/css/leptonChrome.css
index 9be5bd3..3f989da 100644
--- a/css/leptonChrome.css
+++ b/css/leptonChrome.css
@@ -7073,6 +7073,12 @@
       background-color: transparent !important;
     }
   }
+  /* Fix tab overlap #678 */
+  @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner") {
+    tab:where([visuallyselected="true"]) {
+      z-index: 1;
+    }
+  }
 }
 /*= New tab button - Smaller button ==========================================*/
 @supports -moz-bool-pref("userChrome.tab.newtab_button_smaller") {
diff --git a/src/tab/newtab_button/_looks_like_tab.scss b/src/tab/newtab_button/_looks_like_tab.scss
index 3b6de4f..ef6e103 100644
--- a/src/tab/newtab_button/_looks_like_tab.scss
+++ b/src/tab/newtab_button/_looks_like_tab.scss
@@ -143,3 +143,10 @@
     // background-position: center;
   }
 }
+
+/* Fix tab overlap #678 */
+@include Option("userChrome.tab.bottom_rounded_corner") {
+  tab:where([visuallyselected="true"]) {
+    z-index: 1;
+  }
+}