RefRange behavior

[Alex]

Hi all,
given this:

´´´
import std.range;

size_t[] arr;

struct S
{
	RefRange!(size_t[]) member;
}

void fun(ref size_t numByRef){}

void main()
{
	arr.length = 42;
	S s;
	s.member = refRange(&arr);
	static assert(__traits(compiles, fun(s.member[0])));
	static assert(!__traits(compiles, fun(s.member.front)));
	//fun(s.member.front);
	/*
	source/app.d(19,5): Error: function `app.fun(ref ulong 
numByRef)` is not callable using argument types `(ulong)`
	source/app.d(19,5):        cannot pass rvalue argument 
`s.member.front()` of type `ulong` to parameter `ref ulong 
numByRef`
	*/
}
´´´

Why does the last static assert yields false? Is there a simple 
workaround, maybe?