Index: wp-includes/query.php
===================================================================
--- wp-includes/query.php	(revision 22238)
+++ wp-includes/query.php	(working copy)
@@ -2725,7 +2725,7 @@
 			}
 
 			if ( $this->is_preview && $this->posts && current_user_can( $edit_cap, $this->posts[0]->ID ) )
-				$this->posts[0] = apply_filters_ref_array('the_preview', array( $this->posts[0], &$this ));
+				$this->posts[0] = get_post( apply_filters_ref_array( 'the_preview', array( $this->posts[0], &$this ) ) );
 		}
 
 		// Put sticky posts at the top of the posts array