wp_create_nonce() returns the same every time

Hey.

I am getting a nonce through admin-ajax.php like this:

add_action('wp_ajax_test_ajax', 'test_ajax');
function test_ajax(){
	global $wpdb;
	echo $nonce = wp_create_nonce();
	echo wp_verify_nonce($nonce);
	die('It worked. Wo - ho.');
}

But that always return the same value, and this is really frustrating, because it’s not supposed to be like that.

Any help would be appreciated greatly.