diff --git a/lib/closure_tree/acts_as_tree.rb b/lib/closure_tree/acts_as_tree.rb
index 84ac93e5..dae75453 100644
--- a/lib/closure_tree/acts_as_tree.rb
+++ b/lib/closure_tree/acts_as_tree.rb
@@ -50,7 +50,9 @@ def ==(comparison_object)
         :class_name => ct_class.to_s,
         :foreign_key => parent_column_name
 
-      attr_accessible :parent
+      unless defined?(ActiveModel::ForbiddenAttributesProtection) && ancestors.include?(ActiveModel::ForbiddenAttributesProtection)
+        attr_accessible :parent
+      end
 
       has_many :children, with_order_option(
         :class_name => ct_class.to_s,