diff --git a/lib/acts_as_tree.rb b/lib/acts_as_tree.rb
index 64460ee..e711e1b 100644
--- a/lib/acts_as_tree.rb
+++ b/lib/acts_as_tree.rb
@@ -65,7 +65,7 @@ module ClassMethods
     #                            a custom column by passing a symbol or string.
     def acts_as_tree(options = {})
       configuration = {
-        primary_key:   primary_key,
+        primary_key:   "id",
         foreign_key:   "parent_id",
         order:         nil,
         counter_cache: nil,