Index: wp-admin/css/wp-admin-rtl.dev.css
===================================================================
--- wp-admin/css/wp-admin-rtl.dev.css (revision 19414)
+++ wp-admin/css/wp-admin-rtl.dev.css (working copy)
@@ -367,6 +367,17 @@
 	left: 170px;
 	right: 150px;
 }
+#contextual-help-back.contextual-help-back-no-sidebar {
+	-webkit-border-bottom-right-radius: 0;
+	border-bottom-right-radius: 0;
+	-webkit-border-bottom-left-radius: 2px;
+	border-bottom-left-radius: 2px;
+	border-right-width: 1px;
+	border-left-width: 0;
+	left: 0;
+	right: 150px;
+}
+
 
 .contextual-help-tabs {
 	float: right;
Index: wp-admin/css/wp-admin.dev.css
===================================================================
--- wp-admin/css/wp-admin.dev.css (revision 19414)
+++ wp-admin/css/wp-admin.dev.css (working copy)
@@ -1468,6 +1468,13 @@
 	border-width: 0 1px;
 	border-style: solid;
 }
+#contextual-help-back.contextual-help-back-no-sidebar {
+	-webkit-border-bottom-right-radius: 2px;
+	border-bottom-right-radius: 2px;
+	border-right-width: 0;
+	right: 0;
+}
+
 
 .contextual-help-tabs {
 	float: left;
Index: wp-admin/includes/screen.php
===================================================================
--- wp-admin/includes/screen.php (revision 19414)
+++ wp-admin/includes/screen.php (working copy)
@@ -704,7 +704,7 @@
 		<div id="screen-meta" class="metabox-prefs">
 			
 			<div id="contextual-help-wrap" class="hidden">
-				<div id="contextual-help-back"></div>
+				<div id="contextual-help-back"<?php if ( empty( $this->_help_sidebar ) ) : echo ' class="contextual-help-back-no-sidebar"'; endif; ?>></div>
 				<div id="contextual-help-columns">
 					<div class="contextual-help-tabs">
 						<ul>