Index: wp-includes/nav-menu.php
===================================================================
--- wp-includes/nav-menu.php	(revision 18736)
+++ wp-includes/nav-menu.php	(working copy)
@@ -618,10 +618,8 @@
 			$menu_item->target = empty( $menu_item->target ) ? get_post_meta( $menu_item->ID, '_menu_item_target', true ) : $menu_item->target;
 
 			$menu_item->attr_title = empty( $menu_item->attr_title ) ? apply_filters( 'nav_menu_attr_title', $menu_item->post_excerpt ) : $menu_item->attr_title;
+			$menu_item->description = empty( $menu_item->description ) ? apply_filters( 'nav_menu_description', $menu_item->post_content ) : $menu_item->description;
 
-			if ( empty( $menu_item->description ) )
-				$menu_item->description = apply_filters( 'nav_menu_description',  wp_trim_words( $menu_item->post_content, 200 ) );
-
 			$menu_item->classes = empty( $menu_item->classes ) ? (array) get_post_meta( $menu_item->ID, '_menu_item_classes', true ) : $menu_item->classes;
 			$menu_item->xfn = empty( $menu_item->xfn ) ? get_post_meta( $menu_item->ID, '_menu_item_xfn', true ) : $menu_item->xfn;
 		} else {
@@ -669,6 +667,22 @@
 }
 
 /**
+ * Trim a nav menu item description to 200 words.
+ *
+ * Hooked into the nav_menu_description filter.
+ *
+ * @access private
+ * @since 3.3.0
+ *
+ * @param string $description The full length description.
+ * @return string Trimmed description.
+ */
+function _wp_trim_nav_menu_description( $description ) {
+	return ! empty( $description ) ? wp_trim_words( $description, 200 ) : '';
+}
+add_filter( 'nav_menu_description', '_wp_trim_nav_menu_description' );
+
+/**
  * Get the menu items associated with a particular object.
  *
  * @since 3.0.0