diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index 7d5781b23a..73f2e94cd1 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -361,7 +361,7 @@ module ActionController
   #         # It's mandatory to specify the nested attributes that should be whitelisted.
   #         # If you use `permit` with just the key that points to the nested attributes hash,
   #         # it will return an empty hash.
-  #         params.require(:person).permit(:name, :age, pets_attributes: { :name, :category })
+  #         params.require(:person).permit(:name, :age, pets_attributes: [ :name, :category ])
   #       end
   #   end
   #