diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index 44703221f32bd..b279ef81a9d20 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -201,6 +201,7 @@ def require(key)
     # You may declare that the parameter should be an array of permitted scalars
     # by mapping it to an empty array:
     #
+    #   params = ActionController::Parameters.new(tags: ['rails', 'parameters'])
     #   params.permit(tags: [])
     #
     # You can also use +permit+ on nested parameters, like: