diff --git a/doc/function_output_iterator_ref.rst b/doc/function_output_iterator_ref.rst
index b346b0d..f46a91c 100644
--- a/doc/function_output_iterator_ref.rst
+++ b/doc/function_output_iterator_ref.rst
@@ -9,7 +9,9 @@
     typedef void                     pointer;
     typedef void                     reference;
 
-    explicit function_output_iterator(const UnaryFunction& f = UnaryFunction());
+    explicit function_output_iterator();
+
+    explicit function_output_iterator(const UnaryFunction& f);
 
     /* see below */ operator*();
     function_output_iterator& operator++();