Wrong use of "classes" attribute to action_link in activity_navigation class

For the activity_navigation class.
Into the attributes list for the action_link, the CSS class value is set into the "classes" key. However, the action_link class require it value in "class" key.

In the method action_link->export_for_template exists the nex line:

$data->classes = isset($attributes['class']) ? $attributes['class'] : '';

The "class" key is checked and it is assigned to "classes" attribute.