Lua and Exceptions

I'm using Lua together with luabind and have problems with exceptions. I execute a lua script that calls some c++ code. This code throws an exception. I use a lua_pcall with the following errorhandler : int LuaErrorHandler( lua_State* L ) { int sz = lua_gettop( L ); cout << "LUA: Error" << endl; cout << "LUA: " << lua_tostring( L, -1 ) << endl; return 0; } This just reports: LUA: Error LUA: Unknown Exception. My problem is that I would like to get the message that the exception was created with(e.what()) and I'm not sure how to do this. Is it necessary to upgrade lua to 5.1 instead of 5.02 as I currently use? Thanks Niels