How do you deserialize XML when you don't know the namespace?

I am dealing with an API that occasionally changes the namespaces on the XML that I receive. The XML structure remains the same. I need to deserialize the XML into a strongly typed model.

How do I perform the deserialization regardless of what namespace is on the XML?

I was using a model like this:

[Serializable, XmlRoot(ElementName = "TestModel", Namespace = "http://ift.tt/1B24abW")]
public class TestModel
{
    public TestModel()
    {
        TestElements = new List<TestModelChildren>();
    }

    [XmlElement("TestModelChildren")]
    public List<TestModelChildren> TestElements { get; set; }
}

I try to deserialize some XML into that model with code like this:

public TestModel DeserializeIt(XDocument xDoc)
{
    TestModel result;
    var serializer = new XmlSerializer(typeof(TestModel));

    using(var sr = new StringReader(xDoc.ToString()))
    {
        result = (TestModel)serializer.Deserialize(sr);
    }

    return result;
}

My problem is that every so often, the namespace on the XML I am receiving changes. I might start getting XML like this:

<TestModel xmlns:i="http://ift.tt/ra1lAU" xmlns="http://ift.tt/1D4bTLs">
    <TestModelChildren>
        ...
    </TestModelChildren>
</TestModel>

I don't want to have to recompile my code every time this namespace change happens. How do I deal with it?