diff --git a/include/boost/iostreams/device/mapped_file.hpp b/include/boost/iostreams/device/mapped_file.hpp
index 0f239bd..e04830c 100755
--- a/include/boost/iostreams/device/mapped_file.hpp
+++ b/include/boost/iostreams/device/mapped_file.hpp
@@ -63,18 +63,18 @@ struct mapped_file_impl;
 struct mapped_file_params {
     explicit mapped_file_params()
         : mode(), offset(0), length(static_cast<std::size_t>(-1)),
-          size(0), hint(0)
+          new_file_size(0), hint(0)
         { }
     explicit mapped_file_params(const std::string& path)
         : path(path), mode(), offset(0),
           length(static_cast<std::size_t>(-1)),
-          size(0), hint(0)
+          new_file_size(0), hint(0)
         { }
     std::string          path;
     BOOST_IOS::openmode  mode;
     stream_offset        offset;
     std::size_t          length;
-    stream_offset        size;
+    stream_offset        new_file_size;
     const char*          hint;
 };