diff --git a/src/wp-admin/includes/nav-menu.php b/src/wp-admin/includes/nav-menu.php
index 625edaf5ae..017d6258d2 100644
--- a/src/wp-admin/includes/nav-menu.php
+++ b/src/wp-admin/includes/nav-menu.php
@@ -899,10 +899,16 @@ function wp_get_nav_menu_to_edit( $menu_id = 0 ) {
 		 */
 		$walker_class_name = apply_filters( 'wp_edit_nav_menu_walker', 'Walker_Nav_Menu_Edit', $menu_id );
 
-		if ( class_exists( $walker_class_name, false ) )
+		if ( class_exists( $walker_class_name, false ) ) {
 			$walker = new $walker_class_name;
-		else
-			return new WP_Error( 'menu_walker_not_exist', sprintf( __('The Walker class named <strong>%s</strong> does not exist.'), $walker_class_name ) );
+		} else {
+			return new WP_Error( 'menu_walker_not_exist',
+				/* translators: %s: walker class name */
+				sprintf( __( 'The Walker class named %s does not exist.' ),
+					'<strong>' . $walker_class_name . '</strong>'
+				)
+			);
+		}
 
 		$some_pending_menu_items = $some_invalid_menu_items = false;
 		foreach ( (array) $menu_items as $menu_item ) {