HTML5 shows empty input readonly attribute as invalid by Edward D. Brey

The HTML5 validator shows a warning if an <input> element has a "readonly" attribute without a value. The error is "Validation (HTML5): This attribute name must be followed by an equal (=) sign and a value. If the value is in quotation marks, the quotation marks must match."

However, HTML5 allows the readonly attribute to be empty: http://www.w3.org/TR/html-markup/input.text.html#input.text.attrs.readonly