diff --git a/src/iri-parser.lisp b/src/iri-parser.lisp
index 812b715..056353a 100644
--- a/src/iri-parser.lisp
+++ b/src/iri-parser.lisp
@@ -353,7 +353,9 @@
                  (format string-stream "?~a" query))
                (when fragment
                  (format string-stream "#~a" fragment))))))
-    (write-string (render) stream)))
+    (if stream
+        (write-string (render) stream)
+        (render))))
 
 (defmethod to-s ((object iri) &key &allow-other-keys)
   (with-output-to-string (stream)