Is this a bug when creating proxies in classes?

[Gary Willoughby via Digitalmars-d-learn]

Compiling the following code:

        import std.typecons;
        class Foo
        {
                private int foo;

                mixin Proxy!(foo);

                this(int x)
                {
                        this.foo = x;
                }
        }

        void main()
        {
        }

Produces this error:

:!rdmd --force -de -debug -w test.d
/usr/include/dmd/phobos/std/typecons.d(4043): Error: template 
instance isArray!(typeof(a)) template 'isArray' is not defined
test.d(7): Error: mixin test.Foo.Proxy!(foo) error instantiating
Failed: ["dmd", "-de", "-debug", "-w", "-v", "-o-", "test.d", 
"-I."]

Can anyone else confirm or am i doing something wrong. I'm using 
DMD 2.066.0 64bit Ubuntu 14.04.