diff --git a/doc/transform_iterator.html b/doc/transform_iterator.html
index ed69c45..2281737 100644
--- a/doc/transform_iterator.html
+++ b/doc/transform_iterator.html
@@ -99,7 +99,7 @@ private:
 </pre>
 <p>If <tt class="docutils literal"><span class="pre">Reference</span></tt> is <tt class="docutils literal"><span class="pre">use_default</span></tt> then the <tt class="docutils literal"><span class="pre">reference</span></tt> member of
 <tt class="docutils literal"><span class="pre">transform_iterator</span></tt> is
-<tt class="docutils literal"><span class="pre">result_of&lt;UnaryFunction(iterator_traits&lt;Iterator&gt;::reference)&gt;::type</span></tt>.
+<tt class="docutils literal"><span class="pre">result_of&lt;const UnaryFunction(iterator_traits&lt;Iterator&gt;::reference)&gt;::type</span></tt>.
 Otherwise, <tt class="docutils literal"><span class="pre">reference</span></tt> is <tt class="docutils literal"><span class="pre">Reference</span></tt>.</p>
 <p>If <tt class="docutils literal"><span class="pre">Value</span></tt> is <tt class="docutils literal"><span class="pre">use_default</span></tt> then the <tt class="docutils literal"><span class="pre">value_type</span></tt> member is
 <tt class="docutils literal"><span class="pre">remove_cv&lt;remove_reference&lt;reference&gt;</span> <span class="pre">&gt;::type</span></tt>.  Otherwise,
@@ -117,10 +117,10 @@ convertible to <tt class="docutils literal"><span class="pre">input_iterator_tag
 <div class="section" id="transform-iterator-requirements">
 <h1><a class="toc-backref" href="#id3"><tt class="docutils literal"><span class="pre">transform_iterator</span></tt> requirements</a></h1>
 <p>The type <tt class="docutils literal"><span class="pre">UnaryFunction</span></tt> must be Assignable, Copy Constructible, and
-the expression <tt class="docutils literal"><span class="pre">f(*i)</span></tt> must be valid where <tt class="docutils literal"><span class="pre">f</span></tt> is an object of
+the expression <tt class="docutils literal"><span class="pre">f(*i)</span></tt> must be valid where <tt class="docutils literal"><span class="pre">f</span></tt> is a const object of
 type <tt class="docutils literal"><span class="pre">UnaryFunction</span></tt>, <tt class="docutils literal"><span class="pre">i</span></tt> is an object of type <tt class="docutils literal"><span class="pre">Iterator</span></tt>, and
 where the type of <tt class="docutils literal"><span class="pre">f(*i)</span></tt> must be
-<tt class="docutils literal"><span class="pre">result_of&lt;UnaryFunction(iterator_traits&lt;Iterator&gt;::reference)&gt;::type</span></tt>.</p>
+<tt class="docutils literal"><span class="pre">result_of&lt;const UnaryFunction(iterator_traits&lt;Iterator&gt;::reference)&gt;::type</span></tt>.</p>
 <p>The argument <tt class="docutils literal"><span class="pre">Iterator</span></tt> shall model Readable Iterator.</p>
 </div>
 <div class="section" id="transform-iterator-models">
diff --git a/doc/transform_iterator_ref.rst b/doc/transform_iterator_ref.rst
index 74347a0..70becc5 100644
--- a/doc/transform_iterator_ref.rst
+++ b/doc/transform_iterator_ref.rst
@@ -41,7 +41,7 @@
 
 If ``Reference`` is ``use_default`` then the ``reference`` member of
 ``transform_iterator`` is
-``result_of<UnaryFunction(iterator_traits<Iterator>::reference)>::type``.
+``result_of<const UnaryFunction(iterator_traits<Iterator>::reference)>::type``.
 Otherwise, ``reference`` is ``Reference``.
 
 If ``Value`` is ``use_default`` then the ``value_type`` member is
@@ -64,10 +64,10 @@ 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.  
 
diff --git a/include/boost/iterator/transform_iterator.hpp b/include/boost/iterator/transform_iterator.hpp
index 86565b8..b79a440 100644
--- a/include/boost/iterator/transform_iterator.hpp
+++ b/include/boost/iterator/transform_iterator.hpp
@@ -46,7 +46,7 @@ namespace boost
         // the function.
         typedef typename ia_dflt_help<
             Reference
-          , result_of<UnaryFunc(typename std::iterator_traits<Iterator>::reference)>
+          , result_of<const UnaryFunc(typename std::iterator_traits<Iterator>::reference)>
         >::type reference;
 
         // To get the default for Value: remove any reference on the
diff --git a/test/transform_iterator_test.cpp b/test/transform_iterator_test.cpp
index 255eab4..3caad2a 100644
--- a/test/transform_iterator_test.cpp
+++ b/test/transform_iterator_test.cpp
@@ -12,6 +12,7 @@
 //       Moved test of transform iterator into its own file. It to
 //       to be in iterator_adaptor_test.cpp.
 
+#include <boost/assert.hpp>
 #include <boost/config.hpp>
 #include <algorithm>
 #include <boost/iterator/transform_iterator.hpp>
@@ -106,12 +107,17 @@ struct polymorphic_mult_functor
 {
     //Implement result_of protocol
     template <class FArgs> struct result;
-    template <class F, class T> struct result<F(T       )> {typedef T type;};
-    template <class F, class T> struct result<F(T&      )> {typedef T type;};
-    template <class F, class T> struct result<F(const T&)> {typedef T type;};
+    template <class F, class T> struct result<const F(T       )> {typedef T type;};
+    template <class F, class T> struct result<const F(T&      )> {typedef T type;};
+    template <class F, class T> struct result<const F(const T&)> {typedef T type;};
+    template <class F, class T> struct result<F(T       )> {typedef void type;};
+    template <class F, class T> struct result<F(T&      )> {typedef void type;};
+    template <class F, class T> struct result<F(const T&)> {typedef void type;};
 
     template <class T> 
     T operator()(const T& _arg) const {return _arg*2;}
+    template <class T> 
+    void operator()(const T& _arg) { BOOST_ASSERT(0); }
 };
 
 int