diff --git a/src/hssg/artifacts/html.lisp b/src/hssg/artifacts/html.lisp
index 369a8d6..328c827 100644
--- a/src/hssg/artifacts/html.lisp
+++ b/src/hssg/artifacts/html.lisp
@@ -70,6 +70,7 @@
                (node (plump:make-element
                        parent (normalize tag)
                        :children (plump:make-child-array (length tail)))))
+          (declare (type list tail))
           (set-attributes node attributes)
           ;; Children will be automatically added to NODE as a side effect
           (loop for child in tail when child do (sexp->plump-tree child node))