Index: modules/aggregator/aggregator.parser.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/aggregator/aggregator.parser.inc,v
retrieving revision 1.10
diff -u -p -r1.10 aggregator.parser.inc
--- modules/aggregator/aggregator.parser.inc	24 Jul 2010 17:42:22 -0000	1.10
+++ modules/aggregator/aggregator.parser.inc	15 Nov 2010 03:38:41 -0000
@@ -125,7 +125,11 @@ function aggregator_parse_feed(&$data, $
     else {
       $item['link'] = $feed->link;
     }
-    $item['guid'] = isset($item['guid']) ? $item['guid'] : '';
+
+    // Atom feeds use ID rather than GUID.
+    if (!isset($item['guid'])) {
+      $item['guid'] = isset($item['id']) ? $item['id'] : '';
+    }
 
     // Atom feeds have a content and/or summary tag instead of a description tag.
     if (!empty($item['content:encoded'])) {