diff --git a/include/boost/btree/detail/index_bases.hpp b/include/boost/btree/detail/index_bases.hpp
index 89668c0..e9d3c2a 100644
--- a/include/boost/btree/detail/index_bases.hpp
+++ b/include/boost/btree/detail/index_bases.hpp
@@ -515,7 +515,11 @@ class index_base : public Base, private noncopyable
     friend class index_base;
 
     index_iterator_type   m_index_iterator;
-    file_type*            m_file;  // 0 for end iterator
+// use original type "boost::btree::extendible_mapped_file"
+// instead of typedef type "file_type" to avoid trouble
+// with the i686-apple-darwin11-llvm-g++-4.2 (gcc)4.2.1 compiler
+//    file_type*            m_file;  // 0 for end iterator
+    boost::btree::extendible_mapped_file* m_file;  // 0 for end iterator
 
     Reference dereference() const
     { 
diff --git a/src/detail/buffer_manager.cpp b/src/detail/buffer_manager.cpp
index abb0012..1ef5dc4 100644
--- a/src/detail/buffer_manager.cpp
+++ b/src/detail/buffer_manager.cpp
@@ -104,7 +104,7 @@ void buffer_manager::data_size(data_size_type sz)
   m_data_size = sz;
   offset_type file_size = binary_file::seek(0, seekdir::end);
   m_buffer_count = static_cast<buffer_count_type>(file_size / sz);
-  if (m_buffer_count * sz != file_size)
+  if (file_size < 0 || m_buffer_count * sz != (std::size_t)file_size)
     BOOST_BUFFER_FILE_THROW(buffer_manager_error(
       "buffer_manager_error: file size error; too large or not multiple of data size: ",
       binary_file::path()));