diff --git a/mozilla/toolkit/skin/mac/scrollbars.css b/mozilla/toolkit/skin/mac/scrollbars.css
index 200b858e950..47182412b46 100644
--- a/mozilla/toolkit/skin/mac/scrollbars.css
+++ b/mozilla/toolkit/skin/mac/scrollbars.css
@@ -38,6 +38,12 @@ scrollbar {
   background-color: white;
 }
 
+/* ::::: square at the corner of two scrollbars ::::: */
+
+scrollcorner {
+  background-color: -moz-Dialog;
+}
+
 /* :::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
 /* ::::::::::::::::::::: MEDIA PRINT :::::::::::::::::::::: */
 /* :::::::::::::::::::::::::::::::::::::::::::::::::::::::: */
diff --git a/mozilla/toolkit/skin/win/scrollbars.css b/mozilla/toolkit/skin/win/scrollbars.css
index 6169981bf0d..449b6feae62 100644
--- a/mozilla/toolkit/skin/win/scrollbars.css
+++ b/mozilla/toolkit/skin/win/scrollbars.css
@@ -90,6 +90,12 @@ scrollbarbutton:hover:active {
   background-position: 1px 2px;
 }
 
+/* ::::: square at the corner of two scrollbars ::::: */
+
+scrollcorner { 
+  background-color: -moz-Dialog;
+}
+
 /* ..... increment .... */
 
 scrollbarbutton[type="increment"] {