The result of boost::make_unfused cannot be assigned to a boost::function object

Question

The following code is a snippet that illustrates the problem:

#include <boost/bind.hpp>
#include <boost/function.hpp>
#include <boost/fusion/functional.hpp>
#include <boost/fusion/container.hpp>

using IntFunc = boost::function<void(int, int)>;
using IntArgs = boost::fusion::vector<int, int>;

void HandleInt(const IntArgs& args)
{
}

void UnfusedTest()
{
  auto f = boost::fusion::make_unfused(boost::bind(&HandleInt, _1));
  IntFunc func = f;
}

When compiled using boost 1.61 it fails with

cannot convert argument 1 from 'int' to 'int &'" error.

I need to return a function object that can be called like this: func(1, 2);

What is wrong and what can I do to fix it?

Thanks!