Posting a <form> to the same page returns a 404

I have this code on page.php

<?php 

	if(array_key_exists('form', $_POST)) {

		$name = $_POST['name'];

		echo $name;

	} else {

?>

<form action="" method="post">

     <p>Name<br />
	<input name="name" type="text"></p>

     <input name="form" type="hidden" />

</form>

<?php } ?>

But when the page is submitted it returns a 404 error, despite the URL being identical between pages. I understand this must have something to do with WordPress querying the page but does any have any idea to get this to work?