How to restrict template functor return and parameter types

My code looks like this:

template<typename F>
void printHello(F f)
{
    f("Hello!");
}

int main() {
    std::string buf;
    printHello([&buf](const char*msg) { buf += msg; });
    printHello([&buf]() { });
}

The question is - how can I restrict the F type to accept only lambdas that have a signature void(const char*), so that the second call to printHello doesn't fail at some obscure place inside printHello but instead on the line that calls printHello incorrectly?