Index: wp-admin/edit-form-advanced.php
===================================================================
--- wp-admin/edit-form-advanced.php     (revision 10437)
+++ wp-admin/edit-form-advanced.php     (working copy)
@@ -539,7 +539,7 @@
 <?php if (isset($_GET['message'])) : ?>
 <div id="message" class="updated fade"><p><?php echo $messages[$_GET['message']]; ?></p></div>
 <?php endif; ?>
-<form name="post" action="post.php" method="post" id="post">
+<form name="post" action="post.php" method="post" id="post" enctype="multipart/form-data">
 <?php

 if ( 0 == $post_ID)