--- boost/algorithm/string/detail/case_conv.hpp.org	2008-06-19 14:07:24.000000000 +0200
+++ boost/algorithm/string/detail/case_conv.hpp	2009-11-19 07:09:36.508901000 +0100
@@ -37,9 +37,9 @@
                 CharT operator ()( CharT Ch ) const
                 {
                     #if defined(__BORLANDC__) && (__BORLANDC__ >= 0x560) && (__BORLANDC__ <= 0x564) && !defined(_USE_OLD_RW_STL)
-                        return std::tolower( Ch);
+                        return std::tolower(static_cast<unsigned char>(Ch));
                     #else
-                        return std::tolower<CharT>( Ch, m_Loc );
+                        return std::tolower<CharT>(static_cast<unsigned char>(Ch), m_Loc );
                     #endif
                 }
             private:
@@ -57,9 +57,9 @@
                 CharT operator ()( CharT Ch ) const
                 {
                     #if defined(__BORLANDC__) && (__BORLANDC__ >= 0x560) && (__BORLANDC__ <= 0x564) && !defined(_USE_OLD_RW_STL)
-                        return std::toupper( Ch);
+                        return std::toupper(static_cast<unsigned char>(Ch));
                     #else
-                        return std::toupper<CharT>( Ch, m_Loc );
+                        return std::toupper(static_cast<unsigned char>(Ch));
                     #endif
                 }
             private: