[cl-who-devel] Is it bug?

Hello, when I evaluation this form, (let ((page-title "title")) (with-html-output-to-string (output-str) (:title page-title) output-str)) it return "<title></title>". I suppose page-title in (:title) form isn't expanded as expected. On the other hand, this form (let ((name "name") (checked t) (value nil)) (with-html-output-to-string (string) (:input :type "checkbox" :name name :checked checked :value value) string)) works as expected. So I suppose only one-tag form (like (:title) or (:br) or (:p)) has this bug. My environment is mac os x.3, lispworks 4.3, cl-who 0.4.0. Thanks for any advance, Hoo.