Is it correct behavior that function closest add string 'closest(selector)' to field this.selector?

Code:

		var form = $('form[name=xxx]').closest('form');
		var x = form.find('[name=users_activity]');
		$(x).live('change', function(){
			alert('OK!');
		});

If I try change value in select list ([name=users_activity]) firebug shows this error:

Error: Syntax error, unrecognized expression: form[name=xxx].closest(form) [name=users_activity]
throw new Error( "Syntax error, unrecognized expression: " + msg );

In jQuery 1.3.2 this example code works good.