How to make compile std::funciton

Let's say I have a type alias like this:

template <typename Arg>
using Func = std::function<void(Arg)>;

It works fine except for the case when Arg is void:

Func<int> f1;
Func<void> f2; // doesn't compile

The second one gives the following compilation error:

error: invalid parameter type ‘void’using Func = std::function<void(Arg)>;
error: in declaration ‘using Func = class std::function<void(Arg)>’

How can I make it work to create alias for std::function<void()> ?