diff --git a/toolkit/skin/win/browser.css b/toolkit/skin/win/browser.css
index 649e62239104..37f5c46260d1 100644
--- a/toolkit/skin/win/browser.css
+++ b/toolkit/skin/win/browser.css
@@ -31,4 +31,8 @@ tabpanels {
 
 tab[busy] > .tab-icon {
   list-style-image: url("chrome://global/skin/icons/loading-anim.gif");
-}
\ No newline at end of file
+}
+
+tab[selected="true"] {
+  font-weight: bold;
+}