HashSet incorrectly reported

[Wernight]

Sample code
-----------------

[Test]
public void SomeTest()
{
    var actual = new HashSet<string>(new[] {"foo", "bar"});
    Assert.That(actual, Is.EquivalentTo(new[] { "fo__", "bar" }));
}

Reported as
-----------------

  Expected: equivalent to < "fo__", "bar" >
  But was: <System.Collections.Generic.HashSet`1[System.String]>

Expected being reported as:
---------------------------------------

  Expected: equivalent to < "fo__", "bar" >
  But was: < "foo", "bar" >

Environment
-----------------

NUnit version 2.5.9.10348