diff --git a/src/Api/Projects.php b/src/Api/Projects.php
index 61f05e27e..932dffdf6 100644
--- a/src/Api/Projects.php
+++ b/src/Api/Projects.php
@@ -27,7 +27,8 @@ class Projects extends AbstractApi
      *     @var bool   $archived                    limit by archived status
      *     @var string $visibility                  limit by visibility public, internal, or private
      *     @var string $order_by                    Return projects ordered by id, name, path, created_at, updated_at,
-     *                                              or last_activity_at fields (default is created_at)
+     *                                              last_activity_at, repository_size, storage_size, packages_size or
+     *                                              wiki_size fields (default is created_at)
      *     @var string $sort                        Return projects sorted in asc or desc order (default is desc)
      *     @var string $search                      return list of projects matching the search criteria
      *     @var bool   $search_namespaces           Include ancestor namespaces when matching search criteria
@@ -60,8 +61,12 @@ public function all(array $parameters = [])
         $resolver->setDefined('visibility')
             ->setAllowedValues('visibility', ['public', 'internal', 'private'])
         ;
+        $orderBy = [
+            'id', 'name', 'path', 'created_at', 'updated_at', 'last_activity_at',
+            'repository_size', 'storage_size', 'packages_size', 'wiki_size',
+        ];
         $resolver->setDefined('order_by')
-            ->setAllowedValues('order_by', ['id', 'name', 'path', 'created_at', 'updated_at', 'last_activity_at'])
+            ->setAllowedValues('order_by', $orderBy)
         ;
         $resolver->setDefined('sort')
             ->setAllowedValues('sort', ['asc', 'desc'])