Index: wp-admin/includes/meta-boxes.php
===================================================================
--- wp-admin/includes/meta-boxes.php	(revision 17347)
+++ wp-admin/includes/meta-boxes.php	(working copy)
@@ -507,7 +507,7 @@
  */
 function post_slug_meta_box($post) {
 ?>
-<label class="screen-reader-text" for="post_name"><?php _e('Slug') ?></label><input name="post_name" type="text" size="13" id="post_name" value="<?php echo esc_attr( $post->post_name ); ?>" />
+<label class="screen-reader-text" for="post_name"><?php _e('Slug') ?></label><input name="post_name" type="text" class="large-text" size="13" id="post_name" value="<?php echo esc_attr( $post->post_name ); ?>" />
 <?php
 }