How can I use IHTMLTxtRange.pasteHTML to paste HTML containing a span with a class?

Question

    Dim selection As IHTMLTxtRange = Doc.selection.createRange()
    selection.pasteHTML("<span class=""header"">" + selection.text + "</span>")

I am using the above code to wrap the selection in span tags but the pastHTML method is removing the quotes around my class name. Is there another way to do this or am I doing something wrong? Thanks!