Can you spot the bug?

Can you spot what will cause the following NUnit test not to run on TeamCity 4.5?

[TestFixture("Testing some cool things")]
public class CoolThingsFixture
{
	[Test]
	public void When_Do_Expect()
	{
		Assert.That(2, Is.EqualTo(1+1));
	}
}

hint: TeamCity list it with the ignored tests, yelling “No suitable constructor was found”