What happened to "checked" attribute in IE11?

The following snippet stopped working after upgrade to Windows 8.1 (hence installation of IE11) -

HTML:

<input id="myCheckBox" type="checkbox" />

JavaScript:

var isChecked = $( "#myCheckBox" ).attr( "checked" ) ? true : false;

Review of the checkbox element under IE development toolbar shows it no longer has "checked" attribute whether it's checked or not.

Is this by design?

Thank you,

Eugene