Ticket #23841: 23841.1.diff

wp-content/themes/twentythirteen/js/functions.js

@@ -51 +51 @@
                 if ( navbarOffset < 0 )
                         navbarOffset = navbar.offset().top - toolbarOffset;
 
-                if ( window.scrollY >= navbarOffset && 644 < window.innerWidth )
+                if ( $( this ).scrollTop() >= navbarOffset && 644 < window.innerWidth )
                         html.addClass( 'navbar-fixed' );
                 else
                         html.removeClass( 'navbar-fixed' );