Hi all, When I evaluate this on the repl, it works as expected: (with-html-output-to-string (*empty-stream*) (:li :id "hello" :class "active" (:a :href "#" "hello"))) "<li id=\"hello\" class=\"active\"><a href=\"#\">hello</a></li>" but when I convert it into a function, then it gives me this: (defun tab (page active) (with-html-output-to-string (*empty-stream*) (:li :id (str page) :class (when (string-equal page active) (str "active")) (:a :href "#" (str page))))) TAB (tab "home" "home") "<lihome id=\"home\"active class=\"active\"><a href=\"#\">home</a></li>" Is there something I am doing wrong? I've already tried substituting str with fmt and esc with no luck. Thanks. Alok