unittest + struct ctorю + nested mixin template + alias

[ref2401]

Version D 2.062

class MyClass
{}

struct MyStruct(T)
if (is(T == class))
{
	string _message = "nothing";

	this(T obj)
	{
		if (obj is null){
			_message = "Null reference message";
		}
		else{
			_message = "All right message";
		}
	}

	mixin Foo!();

	private mixin template Foo()
	{
		void foo() {}
	}
}


unittest
{
	alias MyStruct!MyClass StructType;
	auto inst = StructType(null);

	string msg = inst._message;		// Wrong value!
}


The behavior varies between executions: sometimes msg contains 
empty string, in other times it holds "nothing".
If StructType is replaced with MyStruct!MyClass then everything 
works as expected.
	auto inst = MyStruct!MyClass(null);	// OK

If declaration of the Foo template is moved out of struct 
MyStruct(T) definition, everything works fine too.
This strange behavior is observed only in unittest block, not 
when executed in main().
Am I doing something incorrectly or is this a bug?