transform in stl with gcc4.0.3

I try to complie next code with gcc 4.0.3

#include < iostream >
#include < string >
#include < algorithm >
#include < cctype >
using namespace std;

int main(void)
{
  string tmp("ABC");
  cout << tmp << endl;
  transform(tmp.begin(),
   tmp.end(),
   tmp.begin(),
   tolower);
  cout << tmp << endl;
  return 0;
}

GCC can not accept above codes, compile error happens.

Becuase "tolower" function is not certain type.

So I builded wrapper function of tolower, Compile is succeed.