jQuery - Required checkbox to submit form (simple w/ alert)

gistfile1.js

// checkbox must be checked to submit form
$('#contact-submit').click(function(e) {
	var checked = $('#contact-side :checkbox:checked').length;
	if (checked == 0) {
		alert('Before this form can be sent, you must agree to the disclaimer.');
		e.preventDefault();
	} else {
		$('#contact-side form').submit();	
	}
});