diff --git a/src/wp-content/themes/twentytwelve/js/navigation.js b/src/wp-content/themes/twentytwelve/js/navigation.js
index f7141bff7e..93bc0d3f03 100644
--- a/src/wp-content/themes/twentytwelve/js/navigation.js
+++ b/src/wp-content/themes/twentytwelve/js/navigation.js
@@ -20,15 +20,25 @@
 		return;
 	}
 
+	// Assign an ID for the default page list if no menu is set as Primary.
+	if ( ! menu.id ) {
+		menu.id = 'twentytwelve-page-list-menu';
+	}
+
+	button.setAttribute( 'aria-controls', menu.id );
+	button.setAttribute( 'aria-expanded', 'false' );
+
 	button.onclick = function() {
 		if ( -1 === menu.className.indexOf( 'nav-menu' ) ) {
 			menu.className = 'nav-menu';
 		}
 
 		if ( -1 !== button.className.indexOf( 'toggled-on' ) ) {
+			button.setAttribute( 'aria-expanded', 'false' );
 			button.className = button.className.replace( ' toggled-on', '' );
 			menu.className = menu.className.replace( ' toggled-on', '' );
 		} else {
+			button.setAttribute( 'aria-expanded', 'true' );
 			button.className += ' toggled-on';
 			menu.className += ' toggled-on';
 		}