Index: imagefield.module
===================================================================
--- imagefield.module	(revision 2857)
+++ imagefield.module	(working copy)
@@ -332,7 +332,7 @@
     return '<!-- link to default admin thumb -->';
   }
   $thumb_path = imagefield_file_admin_thumb_path($item);
-  return '<img src="'. file_create_url($thumb_path) .'" title="' . check_plain($item['filename']) . '" />';
+  return '<img src="'. file_create_url($thumb_path) .'" title="' . check_plain($item['filename']) . '"  alt="' . check_plain($item['filename']) . '" />';
 }
 /**
  * @} End defgroup "Theme Callbacks".