diff --git a/src/mirror-img.lisp b/src/mirror-img.lisp
index 850c486..3566ae4 100644
--- a/src/mirror-img.lisp
+++ b/src/mirror-img.lisp
@@ -64,7 +64,7 @@ For example:
     (linked-urls dom :tags tags))))
 
 ;; lquery-dom alist list → nil
-(defun substitute-urls (dom substitution-alist &key (tags '("img")))
+(defun substitute-urls (dom substitution-alist &key (tags *default-tags*))
   "Replace SRC or HREF attributes of certain tags in an LQuery DOM, based on a
 substitution associative list. The substitution alist is made up of cons-cells
 mapping replacee URLs to substition URLs.
@@ -125,10 +125,11 @@ HREF and SRC attributes."
   "Set the SRC or HREF attribute of an LQuery node (based on which attribute is
 already set)."
   (and node
-       (if (lquery-funcs:attr node "src")
-           (lquery-funcs:attr node "src" url))
-       (if (lquery-funcs:attr node "href")
-           (lquery-funcs:attr node "href" url))))
+       (cond ((lquery-funcs:attr node "src")
+              (lquery-funcs:attr node "src" url))
+             ((lquery-funcs:attr node "href")
+              (lquery-funcs:attr node "href" url))
+             ('T node))))