diff --git src/wp-includes/link-template.php src/wp-includes/link-template.php
index eb22284ca3..9f51253cc1 100644
--- src/wp-includes/link-template.php
+++ src/wp-includes/link-template.php
@@ -186,8 +186,9 @@ function get_permalink( $post = 0, $leavename = false ) {
 
 				$category_object = get_term( $category_object, 'category' );
 				$category = $category_object->slug;
-				if ( $parent = $category_object->parent )
-					$category = get_category_parents($parent, false, '/', true) . $category;
+				if ( $category_object->parent ) {
+					$category = get_category_parents( $category_object->parent, false, '/', true ) . $category;
+				}
 			}
 			// show default category in permalinks, without
 			// having to assign it explicitly