std::for_each is not compiling with boost::algorithm::to_lowe

[code_carnage]

Hello,
Do you guys know why this does not compile?
<code>
std::for_each(v.begin(), v.end(), &boost::algorithm::to_lower<string>);
</code>
v is a vector of strings that I want to convert to lowercase.
However, if I have another function

static  void toLowerCase(string &s) 
{
     boost::algorithm::to_lower<string>(s);
}

and do like the following it works..

std::for_each(v.begin(), v.end(), toLowerCase);

compiler is g++
Thanks in advance
-Prashant