Index: boost/iterator/transform_iterator.hpp
===================================================================
--- boost/iterator/transform_iterator.hpp	(revision 71401)
+++ boost/iterator/transform_iterator.hpp	(working copy)
@@ -122,7 +122,7 @@
 
     // Probably should be the initial base class so it can be
     // optimized away via EBO if it is an empty class.
-    UnaryFunc m_f;
+    mutable UnaryFunc m_f;
   };
 
   template <class UnaryFunc, class Iterator>