Default hidden value not saving

I have this:

         [
                'id'         => 'post_status_field',
                'type'       => 'hidden',
                'save_field' => true,
                'std' =>  'new',
            ],

But it is not saving. I changed it to text to check it was populating - it is. Even with text, it does not save. I can work with an if empty statement, but would prefer a solid value. Do you know what could be causing? Every other normal field on the form is saving.