Referencing structs in a foreach

[Alf via Digitalmars-d]

I am wondering what could be the mistake. When trying to modify 
the member of a struct from within a foreach, the changes are 
gone after leaving the loop.

Code:
import std.stdio;

void test()
{
  struct Foo
  {
    int a;
    int b;
  }

  struct Bar
  {
    Foo f1;
    Foo f2;
  }

  Bar bar = {{10, 20}, {10, 20}};

  writefln("Before => f1.a: %d, f1.b: %d - f2.a: %d, f2.b: %d\n", 
bar.f1.a, bar.f1.b, bar.f2.a, bar.f2.b);

  foreach (ref f; [bar.f1, bar.f2])
  {
    f.a++;
    f.b++;
  }

  writefln("After => f1.a: %d, f1.b: %d - f2.a: %d, f2.b: %d\n", 
bar.f1.a, bar.f1.b, bar.f2.a, bar.f2.b);
}

void main()
{
  test();
}

Should print:

Before => f1.a: 10, f1.b: 20 - f2.a: 10, f2.b: 20
After => f1.a: 11, f1.b: 21 - f2.a: 11, f2.b: 21

But prints:

Before => f1.a: 10, f1.b: 20 - f2.a: 10, f2.b: 20
After => f1.a: 10, f1.b: 20 - f2.a: 10, f2.b: 20

Thanks,

Alf