diff --git a/doc/quickbook/transform_iterator.qbk b/doc/quickbook/transform_iterator.qbk
index adf30b8..847ec79 100644
--- a/doc/quickbook/transform_iterator.qbk
+++ b/doc/quickbook/transform_iterator.qbk
@@ -86,7 +86,7 @@ The source code for this example can be found
 
 If `Reference` is `use_default` then the `reference` member of
 `transform_iterator` is[br]
-`result_of<UnaryFunction(iterator_traits<Iterator>::reference)>::type`.
+`result_of<const UnaryFunction(iterator_traits<Iterator>::reference)>::type`.
 Otherwise, `reference` is `Reference`.
 
 
@@ -110,10 +110,10 @@ convertible to `input_iterator_tag`.
 
 
 The type `UnaryFunction` must be Assignable, Copy Constructible, and
-the expression `f(*i)` must be valid where `f` is an object of
+the expression `f(*i)` must be valid where `f` is a const object of
 type `UnaryFunction`, `i` is an object of type `Iterator`, and
 where the type of `f(*i)` must be
-`result_of<UnaryFunction(iterator_traits<Iterator>::reference)>::type`.
+`result_of<const UnaryFunction(iterator_traits<Iterator>::reference)>::type`.
 
 
 The argument `Iterator` shall model Readable Iterator.