Setting the value in OpenXml checkbox word2013

So I have a document that I am editing through a WPF(C#) application. I have successfully edited Plain Text content controls, but now I am stuck checking/unchecking the Checkboxes within the form.

I successfully find the checkbox and set the value and save the document, but the checkboxes that are set to true are never checked within the word document when I open it.

Here is the code that I use to manipulate the checkboxes. NOTE: I access the checkboxes at the tag level, hence the field.parent.parent

private static void SetCheckBox(OpenXmlElement field, bool isChecked)
{
    var checkBox = field.Parent.Parent.Descendants<SdtContentCheckBox>().ToList();
    foreach (var check in checkBox)
    {
        if (isChecked)
        {
            check.Checked.Val = OnOffValues.True;
        }
        else
        {
            check.Checked.Val = OnOffValues.False;
        }
        MessageBox.Show(check.Checked.Val);
    }
}

When I display the values in the MessageBox they display 0/1 for true/false. So they are in fact being set.

Am I doing this properly?